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Sample records for aerosol absorption properties

  1. Identifying Aerosol Type/Mixture from Aerosol Absorption Properties Using AERONET

    NASA Technical Reports Server (NTRS)

    Giles, D. M.; Holben, B. N.; Eck, T. F.; Sinyuk, A.; Dickerson, R. R.; Thompson, A. M.; Slutsker, I.; Li, Z.; Tripathi, S. N.; Singh, R. P.; Zibordi, G.

    2010-01-01

    Aerosols are generated in the atmosphere through anthropogenic and natural mechanisms. These sources have signatures in the aerosol optical and microphysical properties that can be used to identify the aerosol type/mixture. Spectral aerosol absorption information (absorption Angstrom exponent; AAE) used in conjunction with the particle size parameterization (extinction Angstrom exponent; EAE) can only identify the dominant absorbing aerosol type in the sample volume (e.g., black carbon vs. iron oxides in dust). This AAE/EAE relationship can be expanded to also identify non-absorbing aerosol types/mixtures by applying an absorption weighting. This new relationship provides improved aerosol type distinction when the magnitude of absorption is not equal (e.g, black carbon vs. sulfates). The Aerosol Robotic Network (AERONET) data provide spectral aerosol optical depth and single scattering albedo - key parameters used to determine EAE and AAE. The proposed aerosol type/mixture relationship is demonstrated using the long-term data archive acquired at AERONET sites within various source regions. The preliminary analysis has found that dust, sulfate, organic carbon, and black carbon aerosol types/mixtures can be determined from this AAE/EAE relationship when applying the absorption weighting for each available wavelength (Le., 440, 675, 870nm). Large, non-spherical dust particles absorb in the shorter wavelengths and the application of 440nm wavelength absorption weighting produced the best particle type definition. Sulfate particles scatter light efficiently and organic carbon particles are small near the source and aggregate over time to form larger less absorbing particles. Both sulfates and organic carbon showed generally better definition using the 870nm wavelength absorption weighting. Black carbon generation results from varying combustion rates from a number of sources including industrial processes and biomass burning. Cases with primarily black carbon showed

  2. Characterization of Spectral Absorption Properties of Aerosols Using Satellite Observations

    NASA Technical Reports Server (NTRS)

    Torres, O.; Jethva, H.; Bhartia, P. K.; Ahn, C.

    2012-01-01

    The wavelength-dependence of aerosol absorption optical depth (AAOD) is generally represented in terms of the Angstrom Absorption Exponent (AAE), a parameter that describes the dependence of AAOD with wavelength. The AAE parameter is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellitebased method of determining the spectral AAOD of absorbing aerosols. The technique uses high spectral resolution measurements of upwelling radiation from scenes where absorbing aerosols lie above clouds as indicated by the UV Aerosol Index. For those conditions, the satellite measured reflectance (rho lambda) is approximately given by Beer's law rho lambda = rho (sub 0 lambda) e (exp -mtau (sub abs lambda)) where rho(sub 0 lambda) is the cloud reflectance, m is the geometric slant path and tau (sub abs lambda) is the spectral AAOD. The rho (sub 0 lambda) term is determined by means of radiative transfer calculations using as input the cloud optical depth derived as described in Torres et al. [JAS, 2012] that accounts for the effects of aerosol absorption. In the second step, corrections for molecular and aerosol scattering effects are applied to the cloud reflectance term, and the spectral AAOD is then derived by inverting the equation above. The proposed technique will be discussed in detail and application results will be presented. The technique can be easily applied to hyper-spectral satellite measurements that include UV such as OMI, GOME and SCIAMACHY, or to multi-spectral visible measurements by other sensors provided that the aerosol-above-cloud events are easily identified.

  3. Retrieval of Aerosol Absorption Properties from Satellite Observations

    NASA Technical Reports Server (NTRS)

    Torres, Omar; Bhartia, Pawan K.; Jethva, H.; Ahn, Chang-Woo

    2012-01-01

    The Angstrom Absorption Exponent (AAE) is a parameter commonly used to characterize the wavelength-dependence of aerosol absorption optical depth (AAOD). It is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellitebased method of determining the spectral AAOD of absorbing aerosols. The technique uses multi-spectral measurements of upwelling radiation from scenes where absorbing aerosols lie above clouds as indicated by the UV Aerosol Index. For those conditions, the satellite measurement can be explained, using an approximations of Beer's Law (BL), as the upwelling reflectance at the cloud top attenuated by the absorption effects of the overlying aerosol layer. The upwelling reflectance at the cloud-top in an aerosol-free atmospheric column is mainly a function of cloud optical depth (COD). In the proposed method of AAE derivation, the first step is determining COD which is retrieved using a previously developed color-ratio based approach. In the second step, corrections for molecular scattering effects are applied to both the observed ad the calculated cloud reflectance terms, and the spectral AAOD is then derived by an inversion of the BL approximation. The proposed technique will be discussed in detail and application results making use of OMI multi-spectral measurements in the UV-Vis. will be presented.

  4. Organic Aerosols from SÃO Paulo and its Relationship with Aerosol Absorption and Scattering Properties

    NASA Astrophysics Data System (ADS)

    Artaxo, P.; Brito, J. F.; Rizzo, L. V.

    2012-12-01

    The megacity of São Paulo with its 19 million people and 7 million cars is a challenge from the point of view of air pollution. High levels of organic aerosols, PM10, black carbon and ozone and the peculiar situation of the large scale use of ethanol fuel makes it a special case. Little is known about the impact of ethanol on air quality and human health and the increase of ethanol as vehicle fuel is rising worldwide An experiment was designed to physico-chemical properties of aerosols in São Paulo, as well as their optical properties. Aerosol size distribution in the size range of 1nm to 10 micrometers is being measured with a Helsinki University SMPS (Scanning Mobility Particle Sizer), an NAIS (Neutral ion Spectrometer) and a GRIMM OPC (Optical Particle Counter). Optical properties are being measured with a TSI Nephelometer and a Thermo MAAP (Multi Angle Absorption Photometer). A CIMEL sunphotometer from the AERONET network measure the aerosol optical depth. Furthermore, a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) and an Aerosol Chemical Speciation Monitor (ACSM) are used to real-time VOC analysis and aerosol composition, respectively. The ACSM was operated for 3 months continuosly during teh wintertime of 2012. The measured total particle concentration typically varies between 10,000 and 30,000 cm-3 being the lowest late in the night and highest around noon and frequently exceeding 50,000 cm-3. Clear diurnal patterns in aerosol optical properties were observed. Scattering and absorption coefficients typically range between 20 and 100 Mm-1 at 450 nm, and between 10 to 40 Mm-1 at 637 nm, respectively, both of them peaking at 7:00 local time, the morning rush hour. The corresponding single scattering albedo varies between 0.50 and 0.85, indicating a significant contribution of primary absorbing particles to the aerosol population. During the first month a total of seven new particle formation events were observed with growth rates ranging from 9 to 25

  5. An Analysis of AERONET Aerosol Absorption Properties and Classifications Representative of Aerosol Source Regions

    NASA Technical Reports Server (NTRS)

    Giles, David M.; Holben, Brent N.; Eck, Thomas F.; Sinyuk, Aliaksandr; Smirnov, Alexander; Slutsker, Ilya; Dickerson, R. R.; Thompson, A. M.; Schafer, J. S.

    2012-01-01

    Partitioning of mineral dust, pollution, smoke, and mixtures using remote sensing techniques can help improve accuracy of satellite retrievals and assessments of the aerosol radiative impact on climate. Spectral aerosol optical depth (tau) and single scattering albedo (omega (sub 0) ) from Aerosol Robotic Network (AERONET) measurements are used to form absorption [i.e., omega (sub 0) and absorption Angstrom exponent (alpha(sub abs))] and size [i.e., extinction Angstrom exponent (alpha(sub ext)) and fine mode fraction of tau] relationships to infer dominant aerosol types. Using the long-term AERONET data set (1999-2010), 19 sites are grouped by aerosol type based on known source regions to: (1) determine the average omega (sub 0) and alpha(sub abs) at each site (expanding upon previous work); (2) perform a sensitivity study on alpha(sub abs) by varying the spectral omega (sub 0); and (3) test the ability of each absorption and size relationship to distinguish aerosol types. The spectral omega (sub 0) averages indicate slightly more aerosol absorption (i.e., a 0.0 < delta omega (sub 0) <= 0.02 decrease) than in previous work and optical mixtures of pollution and smoke with dust show stronger absorption than dust alone. Frequency distributions of alpha(sub abs) show significant overlap among aerosol type categories and at least 10% of the alpha(sub abs) retrievals in each category are below 1.0. Perturbing the spectral omega (sub 0) by +/- 0.03 induces significant alpha(sub abs) changes from the unperturbed value by at least approx. +/- 0.6 for Dust, approx. +/-0.2 for Mixed, and approx. +/-0.1 for Urban/Industrial and Biomass Burning. The omega (sub 0)440nm and alpha(sub ext) 440-870nm relationship shows the best separation among aerosol type clusters, providing a simple technique for determining aerosol type from surface- and future space-based instrumentation.

  6. Light scattering and absorption properties of aerosol particles in the urban environment of Granada, Spain

    NASA Astrophysics Data System (ADS)

    Lyamani, H.; Olmo, F. J.; Alados-Arboledas, L.

    Surface measurements of optical and physical aerosol properties were made at an urban site, Granada (Spain) (37.18°N, 3.58°W, 680 m a.s.l), during winter 2005-2006. Measurements included the aerosol scattering, σsca, and backscattering coefficients, σbsca, at three wavelengths (450, 550 and 700 nm) measured at low relative humidity (RH<50%) by an integrating nephelometer, the absorption coefficient at 670 nm, σabs, measured with a multi-angle absorption photometer, and aerosol size distribution in the 0.5-20 μm aerodynamic diameter range registered by an aerodynamic aerosol sizer (APS-3321, TSI). The hourly average of σsca (550 nm) ranged from 2 to 424 M m -1 with an average value of 84±62 M m -1 (±S.D.). The Angstrom exponent presented an average value of 1.8±0.3, suggesting a large fraction of fine particles at the site, an observation confirmed by aerosol size distribution measurements. The hourly average of σabs (670 nm) ranged from 1.7 to 120.5 M m -1 with an average value of 28±20 M m -1. The results indicate that the aerosol absorption coefficient in Granada was relatively large. The largest σsca value was associated with air masses that passed over heavily polluted European areas and local stagnation conditions. High absorbing aerosol level was obtained during dust transport from North Africa probably due to the presence of hematite. Based on the measured scattering and absorption coefficients, a very low average value of the single scattering albedo of 0.66±0.11 at 670 nm was calculated, suggesting that urban aerosols in this region contain a large fraction of absorbing material. A clear diurnal pattern was observed in scattering and absorption coefficients and particle concentrations with two local maxima occurring in early morning and late evening. This behavior can be explained in terms of local conditions that control the particle sources associated with traffic and upward mixing of the aerosol during the daytime development of a

  7. Investigating cloud absorption effects: Global absorption properties of black carbon, tar balls, and soil dust in clouds and aerosols

    NASA Astrophysics Data System (ADS)

    Jacobson, Mark Z.

    2012-03-01

    This study examines modeled properties of black carbon (BC), tar ball (TB), and soil dust (SD) absorption within clouds and aerosols to understand better Cloud Absorption Effects I and II, which are defined as the effects on cloud heating of absorbing inclusions in hydrometeor particles and of absorbing aerosol particles interstitially between hydrometeor particles at their actual relative humidity (RH), respectively. The globally and annually averaged modeled 550 nm aerosol mass absorption coefficient (AMAC) of externally mixed BC was 6.72 (6.3-7.3) m2/g, within the laboratory range (6.3-8.7 m2/g). The global AMAC of internally mixed (IM) BC was 16.2 (13.9-18.2) m2/g, less than the measured maximum at 100% RH (23 m2/g). The resulting AMAC amplification factor due to internal mixing was 2.41 (2-2.9), with highest values in high RH regions. The global 650 nm hydrometeor mass absorption coefficient (HMAC) due to BC inclusions was 17.7 (10.6-19) m2/g, ˜9.3% higher than that of the IM-AMAC. The 650 nm HMACs of TBs and SD were half and 1/190th, respectively, that of BC. Modeled aerosol absorption optical depths were consistent with data. In column tests, BC inclusions in low and mid clouds (CAE I) gave column-integrated BC heating rates ˜200% and 235%, respectively, those of interstitial BC at the actual cloud RH (CAE II), which itself gave heating rates ˜120% and ˜130%, respectively, those of interstitial BC at the clear-sky RH. Globally, cloud optical depth increased then decreased with increasing aerosol optical depth, consistent with boomerang curves from satellite studies. Thus, CAEs, which are largely ignored, heat clouds significantly.

  8. Light absorption properties and radiative effects of primary organic aerosol emissions.

    PubMed

    Lu, Zifeng; Streets, David G; Winijkul, Ekbordin; Yan, Fang; Chen, Yanju; Bond, Tami C; Feng, Yan; Dubey, Manvendra K; Liu, Shang; Pinto, Joseph P; Carmichael, Gregory R

    2015-04-21

    Organic aerosols (OAs) in the atmosphere affect Earth's energy budget by not only scattering but also absorbing solar radiation due to the presence of the so-called "brown carbon" (BrC) component. However, the absorptivities of OAs are not represented or are poorly represented in current climate and chemical transport models. In this study, we provide a method to constrain the BrC absorptivity at the emission inventory level using recent laboratory and field observations. We review available measurements of the light-absorbing primary OA (POA), and quantify the wavelength-dependent imaginary refractive indices (kOA, the fundamental optical parameter determining the particle's absorptivity) and their uncertainties for the bulk POA emitted from biomass/biofuel, lignite, propane, and oil combustion sources. In particular, we parametrize the kOA of biomass/biofuel combustion sources as a function of the black carbon (BC)-to-OA ratio, indicating that the absorptive properties of POA depend strongly on burning conditions. The derived fuel-type-based kOA profiles are incorporated into a global carbonaceous aerosol emission inventory, and the integrated kOA values of sectoral and total POA emissions are presented. Results of a simple radiative transfer model show that the POA absorptivity warms the atmosphere significantly and leads to ∼27% reduction in the amount of the net global average POA cooling compared to results from the nonabsorbing assumption. PMID:25811601

  9. Light absorption properties and radiative effects of primary organic aerosol emissions.

    PubMed

    Lu, Zifeng; Streets, David G; Winijkul, Ekbordin; Yan, Fang; Chen, Yanju; Bond, Tami C; Feng, Yan; Dubey, Manvendra K; Liu, Shang; Pinto, Joseph P; Carmichael, Gregory R

    2015-04-21

    Organic aerosols (OAs) in the atmosphere affect Earth's energy budget by not only scattering but also absorbing solar radiation due to the presence of the so-called "brown carbon" (BrC) component. However, the absorptivities of OAs are not represented or are poorly represented in current climate and chemical transport models. In this study, we provide a method to constrain the BrC absorptivity at the emission inventory level using recent laboratory and field observations. We review available measurements of the light-absorbing primary OA (POA), and quantify the wavelength-dependent imaginary refractive indices (kOA, the fundamental optical parameter determining the particle's absorptivity) and their uncertainties for the bulk POA emitted from biomass/biofuel, lignite, propane, and oil combustion sources. In particular, we parametrize the kOA of biomass/biofuel combustion sources as a function of the black carbon (BC)-to-OA ratio, indicating that the absorptive properties of POA depend strongly on burning conditions. The derived fuel-type-based kOA profiles are incorporated into a global carbonaceous aerosol emission inventory, and the integrated kOA values of sectoral and total POA emissions are presented. Results of a simple radiative transfer model show that the POA absorptivity warms the atmosphere significantly and leads to ∼27% reduction in the amount of the net global average POA cooling compared to results from the nonabsorbing assumption.

  10. Light Absorption Properties and Radiative Effects of Primary Organic Aerosol Emissions

    EPA Science Inventory

    Organic aerosols (OA) in the atmosphere affect Earth’s energy budget by not only scattering but also absorbing solar radiation due to the presence of the so-called “brown carbon” (BrC) component. However, the absorptivities of OA are not or poorly represented in current climate m...

  11. Absorption Properties of Mediterranean Aerosols Obtained from Multi-year Ground-based and Satellite Remote Sensing Observations

    NASA Technical Reports Server (NTRS)

    Mallet, M.; Dubovik, O.; Nabat, P.; Dulac, F.; Kahn, R.; Sciare, J.; Paronis, D.; Leon, J. F.

    2013-01-01

    Aerosol absorption properties are of high importance to assess aerosol impact on regional climate. This study presents an analysis of aerosol absorption products obtained over the Mediterranean Basin or land stations in the region from multi-year ground-based AERONET and satellite observations with a focus on the Absorbing Aerosol Optical Depth (AAOD), Single Scattering Albedo (SSA) and their spectral dependence. The AAOD and Absorption Angstrom Exponent (AAE) data set is composed of daily averaged AERONET level 2 data from a total of 22 Mediterranean stations having long time series, mainly under the influence of urban-industrial aerosols and/or soil dust. This data set covers the 17 yr period 1996-2012 with most data being from 2003-2011 (approximately 89 percent of level-2 AAOD data). Since AERONET level-2 absorption products require a high aerosol load (AOD at 440 nm greater than 0.4), which is most often related to the presence of desert dust, we also consider level-1.5 SSA data, despite their higher uncertainty, and filter out data with an Angstrom exponent less than 1.0 in order to study absorption by carbonaceous aerosols. The SSA data set includes both AERONET level-2 and satellite level-3 products. Satellite-derived SSA data considered are monthly level 3 products mapped at the regional scale for the spring and summer seasons that exhibit the largest aerosol loads. The satellite SSA dataset includes the following products: (i) Multi-angle Imaging SpectroRadiometer (MISR) over 2000-2011, (ii) Ozone Monitoring Instrument (OMI) near-UV algorithm over 2004-2010, and (iii) MODerate resolution Imaging Spectroradiometer (MODIS) Deep-Blue algorithm over 2005-2011, derived only over land in dusty conditions. Sun-photometer observations show that values of AAOD at 440 nm vary between 0.024 +/- 0.01 (resp. 0.040 +/- 0.01) and 0.050 +/- 0.01 (0.055 +/- 0.01) for urban (dusty) sites. Analysis shows that the Mediterranean urban-industrial aerosols appear "moderately

  12. Absorption and scattering properties of organic carbon versus sulfate dominant aerosols at Gosan climate observatory in Northeast Asia

    NASA Astrophysics Data System (ADS)

    Lim, S.; Lee, M.; Kim, S.-W.; Yoon, S.-C.; Lee, G.; Lee, Y. J.

    2014-08-01

    Carbonaceous and soluble ionic species of PM1.0 and PM10 were measured along with the absorption and scattering properties and aerosol number size distributions at Gosan Climate Observatory (GCO) from January to September 2008. The daily averaged equivalent black carbon (EBC) measured as aerosol absorption exhibited two types of spectral dependence with a distinct maximum (peak) at either 370 nm or 880 nm, by which two subsets were extracted and classified into the respective groups (370 and 880 nm). The 370 nm group was distinguished by high organic carbon (OC) concentrations relative to elemental carbon (EC) and sulfate, but sulfate was predominant for the 880 nm group. The PM1.0 OC of the 370 nm group was mainly composed of refractory and pyrolized components that correlated well with PM1.0 EC1, referred to as char EC, which suggests biofuel and biomass combustion as the source of these OC fractions, particularly during winter. The scanning electron microscope (SEM) images and the number size distributions implied that aerosols of the 370 nm group were externally mixed upon transport in fast-moving air masses that passed through the Beijing area in about one day. In contrast, the aerosols of the 880 nm group were characterized by high sulfate concentrations, and seemed to be internally mixed during slow transport over the Yellow Sea region over approximately 2 to 4 days. The absorption and scattering coefficients of the 880 nm group were noticeably higher compared to those of the 370 nm group. The average absorption ångström exponent (AAE) was estimated to be 1.29 and 1.0 for the 370 and 880 nm groups, respectively, in the range 370-950 nm. These results demonstrated that the optical properties of aerosols were intimately linked to chemical composition and mixing state, characteristics determined both by source and atmospheric aging processes. In OC dominant aerosols, absorption was enhanced in the UV region, which was possibly due to refractory and pyrolized

  13. Light absorption, optical and microphysical properties of trajectory-clustered aerosols at two AERONET sites in West Africa

    NASA Astrophysics Data System (ADS)

    Fawole, O. G.; Cai, X.; MacKenzie, A. R.

    2015-12-01

    Aerosol remote sensing techniques and back-trajectory modeling can be combined to identify aerosol types. We have clustered 7 years of AERONET aerosol signals using trajectory analysis to identify dominant aerosol sources at two AERONET sites in West Africa: Ilorin (4.34 oE, 8.32 oN) and Djougou (1.60 oE, 9.76 oN). Of particular interest are air masses that have passed through the gas flaring region in the Niger Delta area, of Nigeria, en-route the AERONET sites. 7-day back trajectories were calculated using the UK UGAMP trajectory model driven by ECMWF wind analyses data. Dominant sources identified, using literature classifications, are desert dust (DD), Biomass burning (BB) and Urban-Industrial (UI). Below, we use a combination of synoptic trajectories and aerosol optical properties to distinguish a fourth source: that due to gas flaring. Gas flaring, (GF) the disposal of gas through stack in an open-air flame, is believed to be a prominent source of black carbon (BC) and greenhouse gases. For these different aerosol source signatures, single scattering albedo (SSA), refractive index , extinction Angstrom exponent (EEA) and absorption Angstrom exponent (AAE) were used to classify the light absorption characteristics of the aerosols for λ = 440, 675, 870 and1020 nm. A total of 1625 daily averages of aerosol data were collected for the two sites. Of which 245 make up the GF cluster for both sites. For GF cluster, the range of fine-mode fraction is 0.4 - 0.7. Average values SSA(λ), for the total and GF clusters are 0.90(440), 0.93(675), 0.95(870) and 0.96(1020), and 0.93(440), 0.92(675), 0.9(870) and 0.9(1020), respectively. Values of for the GF clusters for both sites are 0.62 - 1.11, compared to 1.28 - 1.66 for the remainder of the clusters, which strongly indicates the dominance of carbonaceous particles (BC), typical of a highly industrial area. An average value of 1.58 for the real part of the refractive index at low SSA for aerosol in the GF cluster is also

  14. A method for segregating the optical absorption properties and the mass concentration of winter time urban aerosol

    NASA Astrophysics Data System (ADS)

    Ajtai, T.; Utry, N.; Pintér, M.; Major, B.; Bozóki, Z.; Szabó, G.

    2015-12-01

    A novel in-situ, real time method for the determination of inherent absorption properties of light absorbing carbonaceous particulate matter and its possible application for source apportionment are introduced here. The method is deduced from a two-week campaign under wintry urban conditions during which strong correlation was found between aerosol number size distribution and wavelength dependent optical absorption coefficient (AOC(λ)), measured by a Single Mobility Particle Sizer (SMPS) and a multi-wavelength photoacoustic absorption spectrometer, respectively, while wood burning and traffic (i.e. fossil fuel burning) activity were identified to be the dominant sources of carbonaceous particulate. Indeed, during the whole campaign, regardless of the actual emission strength of the aerosol sources, the measured number size distributions were always dominated by two unimodal modes with Count Mean Diameter (CMD) of 20 and 100 nm, which could be correlated to traffic and wood burning activities, respectively. AAEff, AAEwb (i.e. the Aerosol Angström Exponent of traffic and wood burning aerosol, respectively), σff(266 nm), σff(1064 nm), σwb(266 nm) and σff(1064 nm) (i.e. the segregated mass specific optical absorption coefficients at two of the measurement wavelengths) were found to be 1.17 ± 0.18, 2.6 ± 0.14, 7.3 ± 0.3 m2g-1, 1.7 ± 0.1 m2g-1 3.4 ± 0.3 m2g-1 and 0.31 ± 0.08 m2g-1, respectively. Furthermore the introduced methodology can also disentangle and quantify the temporal variation of both the segregated optical absorptions and the segregated mass concentrations of traffic and wood burning aerosol. Accordingly, the contribution of wood burning to optical absorption of PM was found to be negligible at 1064 nm but increased gradually towards the shorter wavelengths and became commensurable with the optical absorption of traffic at 266 nm during the whole measurement period. Furthermore, the contribution of wood burning mass to CM (mass of carbonaceous

  15. Scattering and absorption properties of near-surface aerosol over Gangetic-Himalayan region: the role of boundary-layer dynamics and long-range transport

    NASA Astrophysics Data System (ADS)

    Dumka, U. C.; Kaskaoutis, D. G.; Srivastava, M. K.; Devara, P. C. S.

    2015-02-01

    Light scattering and absorption properties of atmospheric aerosols are of vital importance for evaluating their types, sources and radiative forcing. This is of particular interest over the Gangetic-Himalayan (GH) region due to uplift of aerosol from the plains to the Himalayan range, causing serious effects on atmospheric heating, glaciology and monsoon circulation. In this respect, the Ganges Valley Aerosol Experiment (GVAX) was initiated in Nainital from June 2011 to March 2012 with the aim of examining the aerosol properties, source regions, uplift mechanisms and aerosol-radiation-cloud interactions. The present study examines the temporal (diurnal, monthly, seasonal) evolution of scattering (σabsorption (σap) coefficients, their wavelength dependence, and the role of the Indo-Gangetic plains (IGP), boundary-layer dynamics (BLD) and long-range transport (LRT) in aerosol evolution via the Atmospheric Radiation Measurement Mobile Facility. The analysis is separated for particles <10 μm and <1 μm in diameter in order to examine the influence of particle size on optical properties. The σsp and σap exhibit a pronounced seasonal variation between the monsoon low and post-monsoon (November) high, while the scattering wavelength exponent exhibits higher values during the monsoon, in contrast to the absorption Ångström exponent which maximizes in December-March. The elevated-background measuring site provides the advantage of examining the LRT of natural and anthropogenic aerosols from the IGP and southwest Asia and the role of BLD in the aerosol lifting processes. The results reveal higher aerosol concentrations at noontime along with an increase in mixing height, suggesting influence from IGP. The locally emitted aerosols present higher wavelength dependence of the absorption in October-March compared to the rather well-mixed and aged transported aerosols. Monsoon rainfall and seasonally changing air masses contribute to the alteration of the

  16. Shortwave Radiative Fluxes, Solar-Beam Transmissions, and Aerosol Properties: TARFOX and ACE-2 Find More Absorption from Flux Radiometry than from Other Measurements

    NASA Technical Reports Server (NTRS)

    Russell, Philip B.; Redemann, J.; Schmid, B.; Livingston, J. M.; Bergstrom, R. W.; Ramirez, S. A.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    The Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the Second Aerosol Characterization Experiment (ACE-2) made simultaneous measurements of shortwave radiative fluxes, solar-beam transmissions, and the aerosols affecting those fluxes and transmissions. Besides the measured fluxes and transmissions, other obtained properties include aerosol scattering and absorption measured in situ at the surface and aloft; aerosol single scattering albedo retrieved from skylight radiances; and aerosol complex refractive index derived by combining profiles of backscatter, extinction, and size distribution. These measurements of North Atlantic boundary layer aerosols impacted by anthropogenic pollution revealed the following characteristic results: (1) Better agreement among different types of remote measurements of aerosols (e.g., optical depth, extinction, and backscattering from sunphotometers, satellites, and lidars) than between remote and in situ measurements; 2) More extinction derived from transmission measurements than from in situ measurements; (3) Larger aerosol absorption inferred from flux radiometry than from other measurements. When the measured relationships between downwelling flux and optical depth (or beam transmission) are used to derive best-fit single scattering albedos for the polluted boundary layer aerosol, both TARFOX and ACE-2 yield midvisible values of 0.90 +/- 0.04. The other techniques give larger single scattering albedos (i.e. less absorption) for the polluted boundary layer, with a typical result of 0.95 +/- 0.04. Although the flux-based results have the virtue of describing the column aerosol unperturbed by sampling, they are subject to questions about representativeness and other uncertainties (e.g., unknown gas absorption). Current uncertainties in aerosol single scattering albedo are large in terms of climate effects. They also have an important influence on aerosol optical depths retrieved from satellite radiances

  17. Optical properties and chemical composition of aerosol particles at an urban location: An estimation of the aerosol mass scattering and absorption efficiencies

    NASA Astrophysics Data System (ADS)

    Titos, G.; Foyo-Moreno, I.; Lyamani, H.; Querol, X.; Alastuey, A.; Alados-Arboledas, L.

    2012-02-01

    We investigated aerosol optical properties, mass concentration and chemical composition over a 1 year period (from March 2006 to February 2007) at an urban site in Southern Spain (Granada, 37.18°N, 3.58°W, 680 m above sea level). Light-scattering and absorption measurements were performed using an integrating nephelometer and a MultiAngle Absorption Photometer (MAAP), respectively, with no aerosol size cut-off and without any conditioning of the sampled air. PM10 and PM1 (ambient air levels of atmospheric particulate matter finer than 10 and 1 microns) were collected with two high volume samplers, and the chemical composition was investigated for all samples. Relative humidity (RH) within the nephelometer was below 50% and the weighting of the filters was also at RH of 50%. PM10 and PM1 mass concentrations showed a mean value of 44 ± 19 μg/m3 and 15 ± 7 μg/m3, respectively. The mineral matter was the major constituent of the PM10-1 fraction (contributing more than 58%) whereas organic matter and elemental carbon (OM+EC) contributed the most to the PM1 fraction (around 43%). The absorption coefficient at 550 nm showed a mean value of 24 ± 9 Mm-1 and the scattering coefficient at 550 nm presented a mean value of 61 ± 25 Mm-1, typical of urban areas. Both the scattering and the absorption coefficients exhibited the highest values during winter and the lowest during summer, due to the increase in the anthropogenic contribution and the lower development of the convective mixing layer during winter. A very low mean value of the single scattering albedo of 0.71 ± 0.07 at 550 nm was calculated, suggesting that urban aerosols in this site contain a large fraction of absorbing material. Mass scattering and absorption efficiencies of PM10 particles exhibited larger values during winter and lower during summer, showing a similar trend to PM1 and opposite to PM10-1. This seasonality is therefore influenced by the variations on PM composition. In addition, the mass

  18. Aerosol Absorption Measurements in MILAGRO.

    NASA Astrophysics Data System (ADS)

    Gaffney, J. S.; Marley, N. A.; Arnott, W. P.; Paredes-Miranda, L.; Barnard, J. C.

    2007-12-01

    During the month of March 2006, a number of instruments were used to determine the absorption characteristics of aerosols found in the Mexico City Megacity and nearby Valley of Mexico. These measurements were taken as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City (MAX-Mex) that was carried out in collaboration with the Megacity Interactions: Local and Global Research Observations (MILAGRO) campaign. MILAGRO was a joint effort between the DOE, NSF, NASA, and Mexican agencies aimed at understanding the impacts of a megacity on the urban and regional scale. A super-site was operated at the Instituto Mexicano de Petroleo in Mexico City (designated T-0) and at the Universidad Technologica de Tecamac (designated T-1) that was located about 35 km to the north east of the T-0 site in the State of Mexico. A third site was located at a private rancho in the State of Hidalgo approximately another 35 km to the northeast (designated T-2). Aerosol absorption measurements were taken in real time using a number of instruments at the T-0 and T-1 sites. These included a seven wavelength aethalometer, a multi-angle absorption photometer (MAAP), and a photo-acoustic spectrometer. Aerosol absorption was also derived from spectral radiometers including a multi-filter rotating band spectral radiometer (MFRSR). The results clearly indicate that there is significant aerosol absorption by the aerosols in the Mexico City megacity region. The absorption can lead to single scattering albedo reduction leading to values below 0.5 under some circumstances. The absorption is also found to deviate from that expected for a "well-behaved" soot anticipated from diesel engine emissions, i.e. from a simple 1/lambda wavelength dependence for absorption. Indeed, enhanced absorption is seen in the region of 300-450 nm in many cases, particularly in the afternoon periods indicating that secondary organic aerosols are contributing to the aerosol absorption. This is likely due

  19. Scattering and absorption properties of near-surface aerosol over Gangetic-Himalayan region: the role of boundary layer dynamics and long-range transport

    NASA Astrophysics Data System (ADS)

    Dumka, U. C.; Kaskaoutis, D. G.; Srivastava, M. K.; Devara, P. C. S.

    2014-08-01

    Knowledge of light scattering and absorption properties of atmospheric aerosols is of vital importance in evaluating their types, sources and radiative forcing. This is of particular interest over the Gangetic-Himalayan (GH) region due to large aerosol loading over the plains and the uplift over the Himalayan range causing serious effects on atmospheric heating, glaciology and monsoon circulation. In this respect, Ganges Valley Aerosol Experiment (GVAX) was initiated over the region aiming to examine the aerosol properties, source regions, uplift mechanisms and aerosol-cloud interactions. The present study examines the temporal (monthly, seasonal) evolution of scattering (σsp) and absorption (σap) coefficients, their wavelength dependence, and the role of the Indo-Gangetic plains (IGP), boundary-layer dynamics (BLD) and long-range transport (LRT) in the aerosol uplift over the Himalayas. The measurements are performed at the elevated site Nainital via the Atmospheric Radiation Measurement Mobile Facility including several instruments (Nephelometer, Particle Soot Absorption Photometer, etc.) during June 2011 to March 2012. The σsp and σap exhibit a pronounced seasonal variation with monsoon low and post-monsoon (November) high, while the scattering wavelength exponent exhibits higher values during monsoon, in contrast to the absorption Ångström exponent which maximizes in December-March. The analysis is performed separately for particles bellow 10 and 1μm in diameter in order to examine the influence of the particle size on optical properties. The elevated-background measuring site provides the advantage of examining the LRT of natural and anthropogenic aerosols from the IGP and southwest Asia and the role of BLD in the aerosol lifting processes, while the aerosols are found to be well-mixed and aged-type dominant.

  20. Aqueous aerosol SOA formation: impact on aerosol physical properties.

    PubMed

    Woo, Joseph L; Kim, Derek D; Schwier, Allison N; Li, Ruizhi; McNeill, V Faye

    2013-01-01

    Organic chemistry in aerosol water has recently been recognized as a potentially important source of secondary organic aerosol (SOA) material. This SOA material may be surface-active, therefore potentially affecting aerosol heterogeneous activity, ice nucleation, and CCN activity. Aqueous aerosol chemistry has also been shown to be a potential source of light-absorbing products ("brown carbon"). We present results on the formation of secondary organic aerosol material in aerosol water and the associated changes in aerosol physical properties from GAMMA (Gas-Aerosol Model for Mechanism Analysis), a photochemical box model with coupled gas and detailed aqueous aerosol chemistry. The detailed aerosol composition output from GAMMA was coupled with two recently developed modules for predicting a) aerosol surface tension and b) the UV-Vis absorption spectrum of the aerosol, based on our previous laboratory observations. The simulation results suggest that the formation of oligomers and organic acids in bulk aerosol water is unlikely to perturb aerosol surface tension significantly. Isoprene-derived organosulfates are formed in high concentrations in acidic aerosols under low-NO(x) conditions, but more experimental data are needed before the potential impact of these species on aerosol surface tension may be evaluated. Adsorption of surfactants from the gas phase may further suppress aerosol surface tension. Light absorption by aqueous aerosol SOA material is driven by dark glyoxal chemistry and is highest under high-NO(x) conditions, at high relative humidity, in the early morning hours. The wavelength dependence of the predicted absorption spectra is comparable to field observations and the predicted mass absorption efficiencies suggest that aqueous aerosol chemistry can be a significant source of aerosol brown carbon under urban conditions. PMID:24601011

  1. Adhesion of Mineral and Soot Aerosols can Strongly Affect their Scattering and Absorption Properties

    NASA Technical Reports Server (NTRS)

    Mishchenko, Michael I.; Dlugach, Jana M.

    2012-01-01

    We use the numerically exact superposition T-matrix method to compute the optical cross sections and the Stokes scattering matrix for polydisperse mineral aerosols (modeled as homogeneous spheres) covered with a large number of much smaller soot particles. These results are compared with the Lorenz-Mie results for a uniform external mixture of mineral and soot aerosols. We show that the effect of soot particles adhering to large mineral particles can be to change the extinction and scattering cross sections and the asymmetry parameter quite substantially. The effect on the phase function and degree of linear polarization can be equally significant.

  2. Light absorption properties of water soluble organic aerosol from Residential Wood Burning in Fresno, CA: Results from 2013 NASA DISCOVER-AQ Campaign

    NASA Astrophysics Data System (ADS)

    Kim, H.; Zhang, Q.; Young, D. E.; Parworth, C.

    2015-12-01

    Light absorption properties of water soluble organic aerosol were investigated at Fresno, CA from 13 January to 11 February, 2013 as part of the NASA DISCOVER-AQ campaign. The light absorption spectra of water soluble organic aerosol in PM2.5 was measured using a UV/vis diode array detector (DAD) coupled with a particle into liquid sampler (PILS) that sampled downstream of a PM2.5 cyclone (URG). The PILS was also coupled with two ion chromatographs (IC) to measure inorganic and organic ionic species in PM2.5. In addition, an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was deployed at the same site to measure size-resolved chemical composition of submicrometer aerosol (PM1) in real time during this study. Light absorption at 365 nm (Abs365), which is typically used as a proxy of water-soluble brown carbon (BrC), showed strong enhancement during night time and appeared to correlate well (r = 0.71) with biomass burning organic aerosol (BBOA) from residential wood burning for heating in the Fresno area. The tight correlations between Abs365 and biomass burning relevant tracers such as acetonitrile (r = 0.69), AMS-signature ions for phenolic compounds (r = 0.52-0.71), PAH (r = 0.74), and potassium (r = 0.67) further confirm that biomass burning contributed significantly to water soluble brown carbon during this study. The absorption angstrom exponent (Åa) values fitted between 300 and 700 nm wavelength were 3.3 ± 1.1, 2.0 ± 0.9 and 4.0 ± 0.8, respectively, in the morning, afternoon and nighttime, indicating that BrC is prevalent at night in Fresno during wintertime. However, there are also indications that small amount of BrC existed during the daytime as well, likely due to daytime wood burning and other sources such as the formation of light-absorbing secondary organic aerosol (SOA). Finally, light absorption at 300 nm, 330 nm, and 390 nm were found to correlate tightly with BBOA, which indicate that biomass burning also emits

  3. Wavelength-Dependent Optical Absorption Properties of Artificial and Atmospheric Aerosol Measured by a Multi-Wavelength Photoacoustic Spectrometer

    NASA Astrophysics Data System (ADS)

    Utry, N.; Ajtai, T.; Pintér, M.; Bozóki, Z.; Szabó, G.

    2014-12-01

    Various aspects of the photoacoustic (PA) detection method are discussed from the point of view of developing it into a routine tool for measuring the wavelength-dependent optical absorption coefficient of artificial and atmospheric aerosol. The discussion includes the issues of calibration, cross-sensitivity to gaseous molecules, background PA signal subtraction, and size-dependent particle losses within the PA system. The results in this paper are based on a recently developed four-wavelength PA system, which has operational wavelengths in the near-infrared, in the visible, and in the ultraviolet. The measured spectra of artificial and atmospheric aerosol prove the outstanding applicability of the presented PA system.

  4. Correlations between absorption Angström exponent (AAE) of wintertime ambient urban aerosol and its physical and chemical properties

    NASA Astrophysics Data System (ADS)

    Utry, N.; Ajtai, T.; Filep, Á.; Pintér, M.; Török, Zs.; Bozóki, Z.; Szabó, G.

    2014-07-01

    Based on a two-week measurement campaign in an environment heavily polluted both by transit traffic and household heating in the inner city of Szeged (Hungary), correlations between the absorption Angström exponent (AAE) fitted to the optical absorption coefficients measured with a four wavelength (1064, 532, 355 and 266 nm) photoacoustic aerosol measuring system (4λ-PAS) and various aerosol parameters were identified. AAE was found to depend linearly on OCwb/EC and on NGM100/NGMD20, i.e. on the ratio of mass concentrations of elemental carbon (EC) to the fraction of organic carbon associated with wood burning (OCwb), and on the ratio of aerosol number concentrations in the 20 nm (NGMD20) to 100 nm (NGMD100) modes, with a regression coefficient of R = 0.95 and R = 0.86, respectively. In the daily fluctuation of AAE two minima were identified, which coincide with the morning and afternoon rush hours, during which NGMD20 exhibits maximum values. During the campaign the shape of the aerosol volume size distribution (dV/dlogD) was found to be largely invariant, supporting the assumption that the primary driver for the AAE variation was aerosol chemical composition rather than particle size. Furthermore, when wavelength segregated AAE values were calculated, AAE for the shorter wavelengths (AAE355-266) was also found to depend linearly on the above mentioned ratios with similar regression coefficients but with a much steeper correlation line, while the AAE for the longer wavelengths (AAE1064-532) exhibits only a considerably weaker correlation. These results prove the unique advantages of real time multi-wavelength photoacoustic measurement of optical absorption in case the wavelength range includes the ultra-violet too.

  5. Aerosol optical absorption measurements with photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Kun; Wang, Lei; Liu, Qiang; Wang, Guishi; Tan, Tu; Zhang, Weijun; Chen, Weidong; Gao, Xiaoming

    2015-04-01

    Many parameters related to radiative forcing in climate research are known only with large uncertainties. And one of the largest uncertainties in global radiative forcing is the contribution from aerosols. Aerosols can scatter or absorb the electromagnetic radiation, thus may have negative or positive effects on the radiative forcing of the atmosphere, respectively [1]. And the magnitude of the effect is directly related to the quantity of light absorbed by aerosols [2,3]. Thus, sensitivity and precision measurement of aerosol optical absorption is crucial for climate research. Photoacoustic spectroscopy (PAS) is commonly recognized as one of the best candidates to measure the light absorption of aerosols [4]. A PAS based sensor for aerosol optical absorption measurement was developed. A 532 nm semiconductor laser with an effective power of 160 mW was used as a light source of the PAS sensor. The PAS sensor was calibrated by using known concentration NO2. The minimum detectable optical absorption coefficient (OAC) of aerosol was determined to be 1 Mm-1. 24 hours continues measurement of OAC of aerosol in the ambient air was carried out. And a novel three wavelength PAS aerosol OAC sensor is in development for analysis of aerosol wavelength-dependent absorption Angstrom coefficient. Reference [1] U. Lohmann and J. Feichter, Global indirect aerosol effects: a review, Atmos. Chem. Phys. 5, 715-737 (2005) [2] M. Z. Jacobson, Strong radiative heating due to the mixing state of black carbon in atmospheric aerosols, Nature 409, 695-697 (2001) [3] V. Ramanathan and G. Carmichae, Global and regional climate changes due to black carbon, nature geoscience 1, 221-227 (2008) [4] W.P Arnott, H. Moosmuller, C. F. Rogers, T. Jin, and R. Bruch, Photoacoustic spectrometer for measuring light absorption by aerosol: instrument description. Atmos. Environ. 33, 2845-2852 (1999).

  6. Encapsulation effects on carbonaceous aerosol light absorption

    SciTech Connect

    Sedlacek, A.J.; Onasch, T.; Davidovits, P.; Cross, E.; Mazzoleni, C.

    2010-03-15

    The contribution of aerosol absorption on direct radiative forcing is still an active area of research, in part, because aerosol extinction is dominated by light scattering and, in part, because the primary absorbing aerosol of interest, soot, exhibits complex aging behavior that alters its optical properties. The consequences of this can be evidenced by the work of Ramanathan and Carmichael (2008) who suggest that incorporating the atmospheric heating due to brown clouds (plumes containing soot byproducts from automobiles, biomass burning, wood-burning kitchen stoves, and coal-fired power plants) will increase black carbon (BC) radiative forcing from the Intergovernmental Panel on Climate Change best estimate of 0.34 Wm-2 (±0.25 Wm-2) (IPCC 2007) to 0.9 Wm-2. This noteworthy degree of uncertainty is due largely to the interdependence of BC optical properties on particle mixing state and aggregate morphology, each of which changes as the particle ages in the atmosphere and becomes encapsulated within a coating of inorganic and/or organic substances. In July 2008, a laboratory-based measurement campaign, led by Boston College and Aerodyne, was initiated to begin addressing this interdependence. To achieve insights into the interdependence of BC optical properties on particle mixing state and aggregate morphology, measurements of both the optical and physical properties of flame-generated soot under nascent, coated, and denuded conditions were conducted. This poster presents data on black carbon (BC) light absorption measured by Photothermal Interferometry (Sedlacek and Lee 2007). In addition to examining nascent BC—to provide a baseline measurement—encapsulation with varying thicknesses of either dioctyl sebacate (DOS) or sulfuric acid was conducted to glean insights into the interplay between particle mixing state and optical properties. Additionally, some experiments were carried out where BC was coated and then denuded. In the case of DOS-coated soot, a

  7. Ultraviolet Absorption by Secondary Organic Aerosols

    NASA Astrophysics Data System (ADS)

    Madronich, S.; Lee-Taylor, J. M.; Hodzic, A.; Aumont, B.

    2014-12-01

    Secondary organic aerosols (SOA) are typically formed in the atmosphere by the condensation of a myriad of intermediates from the photo-oxidation of volatile organic compounds (VOCs). Many of these partly oxidized molecules have functional groups (chromophores) that absorb at the ultraviolet (UV) wavelengths available in the troposphere (λ ≳ 290 nm). We used the explicit chemical model GECKO-A (Generator of Explicit Chemistry and Kinetics for Organics in the Atmosphere) to estimate UV absorption cross sections for the gaseous and particulate components of SOA from different precursors (biogenic and anthropogenic) and formed in different environments (low and high NOx, day and night). Model predictions are evaluated with laboratory and field measurements of SOA UV optical properties (esp. mass absorption coefficients and single scattering albedo), and implications are presented for surface UV radiation trends, urban actinic flux modification, and SOA lifetimes.

  8. Spectra Aerosol Light Scattering and Absorption for Laboratory and Urban Aerosol

    NASA Astrophysics Data System (ADS)

    Gyawali, Madhu S.

    Atmospheric aerosols considerably influence the climate, reduce visibility, and cause problems in human health. Aerosol light absorption and scattering are the important factors in the radiation transfer models. However, these properties are associated with large uncertainties in climate modeling. In addition, atmospheric aerosols widely vary in composition and size; their optical properties are highly wavelength dependent. This work presents the spectral dependence of aerosol light absorption and scattering throughout the ultraviolet to near-infrared regions. Data were collected in Reno, NV from 2008 to 2010. Also presented in this study are the aerosol optical and physical properties during carbonaceous aerosols and radiative effects study (CARES) conducted in Sacramento area during 2010. Measurements were made using photoacoustic instruments (PA), including a novel UV 355 nm PA of our design and manufacture. Comparative analyses are presented for three main categories: (1) aerosols produced by wildfires and traffic emissions, (2) laboratory-generated and wintertime ambient urban aerosols, and (3) urban plume and biogenic emissions. In these categories, key questions regarding the light absorption by secondary organic aerosols (SOA), so-called brown carbon (BrC), and black carbon (BC) will be discussed. An effort is made to model the emission and aging of urban and biomass burning aerosol by applying shell-core calculations. Multispectral PA measurements of aerosols light absorption and scattering coefficients were used to calculate the Angstrom exponent of absorption (AEA) and single scattering albedo (SSA). The AEA and SSA values were analyzed to differentiate the aerosol sources. The California wildfire aerosols exhibited strong wavelength dependence of aerosol light absorption with AEA as lambda -1 for 405 and 870 nm, in contrast to the relatively weak wavelength dependence of traffic emissions aerosols for which AEA varied approximately as lambda-1. By using

  9. Spectral dependence of aerosol light absorption over the Amazon Basin

    NASA Astrophysics Data System (ADS)

    Rizzo, L. V.; Correia, A. L.; Artaxo, P.; Procópio, A. S.; Andreae, M. O.

    2011-09-01

    range of 450-880 nm. Further studies should be taken to assess the corresponding impact in the UV spectral range. The assumption that soot spectral properties represent all ambient light absorbing particles may cause a misjudgment of absorption towards the UV, especially in remote areas. Therefore, it is recommended to measure aerosol absorption at several wavelengths to accurately assess the impact of non-soot aerosols on climate and on photochemical atmospheric processes.

  10. Light absorption and morphological properties of soot-containing aerosols observed at an East Asian outflow site, Noto Peninsula, Japan

    NASA Astrophysics Data System (ADS)

    Ueda, S.; Nakayama, T.; Taketani, F.; Adachi, K.; Matsuki, A.; Iwamoto, Y.; Sadanaga, Y.; Matsumi, Y.

    2015-09-01

    The coating of black carbon (BC) with inorganic salts and organic compounds can enhance the magnitude of light absorption by BC. To elucidate the enhancement of light absorption of aged BC particles and its relation to the mixing state and morphology of individual particles, we conducted observations of particles at an Asian outflow site in Noto Peninsula, Japan, in the spring of 2013. Absorption and scattering coefficients at 405, 532, and 781 nm and mass concentrations/mixing states of refractory-BC in PM2.5 were measured using a three-wavelength photoacoustic soot spectrometer and a single-particle soot photometer (SP2), respectively, after passage through a heater maintained at 300 or 400 °C or a bypass line maintained at room temperature (25 °C). The average enhancement of BC light absorption due to coating was estimated by comparing absorption coefficients at 781 nm for particles that with and without passing through the heater and was found to be 22-23 %. The largest enhancements (> 30 %) were observed under high absorption coefficient conditions when the air mass was long-range transported from urban areas in China. Aerosol samples were also analyzed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray analyzer. The morphological features and mixing states of soot-containing particles of four samples collected during the high absorption coefficient events were analyzed by comparing microphotographs before and after the evaporation of beam-sensitive materials by irradiation with a high density electron beam. The majority of the soot in all samples was found as mixed particles with spherical sulfate or as clusters of sulfate spherules. For samples showing high enhancement (> 30 %) of BC light absorption, TEM showed that the internally mixed soot-containing particles tended to have a more spherical shape and to be embedded into the sulfate. The SP2 measurements also suggested that the proportion of thickly-coated soot was

  11. Light absorption and morphological properties of soot-containing aerosols observed at an East Asian outflow site, Noto Peninsula, Japan

    NASA Astrophysics Data System (ADS)

    Ueda, Sayako; Nakayama, Tomoki; Taketani, Fumikazu; Adachi, Kouji; Matsuki, Atsushi; Iwamoto, Yoko; Sadanaga, Yasuhiro; Matsumi, Yutaka

    2016-03-01

    The coating of black carbon (BC) with inorganic salts and organic compounds can enhance the magnitude of light absorption by BC. To elucidate the enhancement of light absorption of aged BC particles and its relation to the mixing state and morphology of individual particles, we conducted observations of particles at an Asian outflow site in Noto Peninsula, Japan, in the spring of 2013. Absorption and scattering coefficients at 405, 532, and 781 nm and mass concentrations/mixing states of refractory BC in PM2.5 were measured using a three-wavelength photoacoustic soot spectrometer and a single-particle soot photometer (SP2), respectively, after passage through a thermodenuder (TD) maintained at 300 or 400 °C or a bypass line maintained at room temperature (25 °C). The average enhancement factor of BC light absorption due to coating was estimated by comparing absorption coefficients at 781 nm for particles that with and without passing through the TD at 300 °C and was found to be 1.22. The largest enhancements (> 1.30) were observed under high absorption coefficient periods when the air mass was long-range transported from urban areas in China. Aerosol samples were also analyzed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray analyzer. The morphological features and mixing states of soot-containing particles of four samples collected during the high absorption events were analyzed by comparing microphotographs before and after the evaporation of beam-sensitive materials by irradiation with a high-density electron beam. The majority of the soot in all samples was found as mixed particles with sulfate-containing spherules or as clusters of such spherules. For samples showing high enhancement (> 1.30) of BC light absorption, the TEM showed that the internally mixed soot-containing particles tended to have a more spherical shape and to be thickly coated. The SP2 measurements also suggested that the proportion of thickly coated

  12. Spectral dependence of aerosol light absorption over the Amazon Basin

    NASA Astrophysics Data System (ADS)

    Rizzo, L. V.; Correia, A. L.; Artaxo, P.; Procópio, A. S.; Andreae, M. O.

    2011-04-01

    assumption that soot spectral properties represent all ambient light absorbing particles may cause a misjudgment of absorption towards the UV, especially in remote areas. Therefore, it is recommended to measure aerosol absorption at several wavelengths from UV to near IR to accurately assess the impact of non-soot aerosols on climate and on photochemical atmospheric processes.

  13. Aerosol Angstrom Absorption Coefficient Comparisons during MILAGRO.

    NASA Astrophysics Data System (ADS)

    Marley, N. A.; Marchany-Rivera, A.; Kelley, K. L.; Mangu, A.; Gaffney, J. S.

    2007-12-01

    Measurements of aerosol absorption were obtained as part of the MAX-Mex component of the MILAGRO field campaign at site T0 (Instituto Mexicano de Petroleo in Mexico City) by using a 7-channel aethalometer (Thermo- Anderson) during the month of March, 2006. The absorption measurements obtained in the field at 370, 470, 520, 590, 660, 880, and 950 nm were used to determine the aerosol Angstrom absorption exponents by linear regression. Since, unlike other absorbing aerosol species (e.g. humic like substances, nitrated PAHs), black carbon absorption is relatively constant from the ultraviolet to the infrared with an Angstrom absorption exponent of -1 (1), a comparison of the Angstrom exponents can indicate the presence of aerosol components with an enhanced UV absorption over that expected from BC content alone. The Angstrom exponents determined from the aerosol absorption measurements obtained in the field varied from - 0.7 to - 1.3 during the study and was generally lower in the afternoon than the morning hours, indicating an increase in secondary aerosol formation and photochemically generated UV absorbing species in the afternoon. Twelve-hour integrated samples of fine atmospheric aerosols (<0.1micron) were also collected at site T0 and T1 (Universidad Technologica de Tecamac, State of Mexico) from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. Samples were collected on quartz fiber filters with high volume impactor samplers. Continuous absorption spectra of these aerosol samples have been obtained in the laboratory from 280 to 900nm with the use of an integrating sphere coupled to a UV spectrometer (Beckman DU with a Labsphere accessory). The integrating sphere allows the detector to collect and spatially integrate the total radiant flux reflected from the sample and therefore allows for the measurement of absorption on highly reflective or diffusely scattering samples. These continuous spectra have also been used to obtain the

  14. The New MODIS-Terra, and the Proposed COBRA Mission: First Global Aerosol Distribution and Properties Over Land and Ocean, and Plans to Measure Global Black Carbon Absorption Over the Ocean Glint

    NASA Technical Reports Server (NTRS)

    Kaufman, Yoram J.; Tanre, Didier; Remer, Lorraine; Martins, Vanderlei; Schoeberl, Mark; Lau, William K. M. (Technical Monitor)

    2001-01-01

    The MODIS instrument was launched on the NASA Terra satellite in Dec. 1999. Since last Oct, the sensor and the aerosol algorithm reached maturity and provide global daily retrievals of aerosol optical thickness and properties. MODIS has 36 spectral channels in the visible to IR with resolution down to 250 m. This allows accurate cloud screening and multi-spectral aerosol retrievals. We derive the aerosol optical thickness over the ocean and most of the land areas, distinguishing between fine (mainly man-made aerosol) and coarse (mainly natural) aerosol particles. New methods to derive the aerosol absorption of sunlight are also being developed. These measurements are use to track different aerosol sources, transport and the radiative forcing at the top and bottom of the atmosphere. However MODIS or any present satellite sensor cannot measure absorption by Black Carbon over the oceans, a critical component in studying climate change and human health. For this purpose we propose the COBRA mission that observes the ocean at glint and off glint simultaneously measuring the spectral polarized light and deriving precisely the aerosol absorption.

  15. Using the OMI aerosol index and absorption aerosol optical depth to evaluate the NASA MERRA Aerosol Reanalysis

    NASA Astrophysics Data System (ADS)

    Buchard, V.; da Silva, A. M.; Colarco, P. R.; Darmenov, A.; Randles, C. A.; Govindaraju, R.; Torres, O.; Campbell, J.; Spurr, R.

    2015-05-01

    A radiative transfer interface has been developed to simulate the UV aerosol index (AI) from the NASA Goddard Earth Observing System version 5 (GEOS-5) aerosol assimilated fields. The purpose of this work is to use the AI and aerosol absorption optical depth (AAOD) derived from the Ozone Monitoring Instrument (OMI) measurements as independent validation for the Modern Era Retrospective analysis for Research and Applications Aerosol Reanalysis (MERRAero). MERRAero is based on a version of the GEOS-5 model that is radiatively coupled to the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) aerosol module and includes assimilation of aerosol optical depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. Since AI is dependent on aerosol concentration, optical properties and altitude of the aerosol layer, we make use of complementary observations to fully diagnose the model, including AOD from the Multi-angle Imaging SpectroRadiometer (MISR), aerosol retrievals from the AErosol RObotic NETwork (AERONET) and attenuated backscatter coefficients from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission to ascertain potential misplacement of plume height by the model. By sampling dust, biomass burning and pollution events in 2007 we have compared model-produced AI and AAOD with the corresponding OMI products, identifying regions where the model representation of absorbing aerosols was deficient. As a result of this study over the Saharan dust region, we have obtained a new set of dust aerosol optical properties that retains consistency with the MODIS AOD data that were assimilated, while resulting in better agreement with aerosol absorption measurements from OMI. The analysis conducted over the southern African and South American biomass burning regions indicates that revising the spectrally dependent aerosol absorption properties in the near-UV region improves the modeled-observed AI comparisons

  16. Climatology of aerosol optical properties and black carbon mass absorption cross section at a remote high-altitude site in the western Mediterranean Basin

    NASA Astrophysics Data System (ADS)

    Pandolfi, M.; Ripoll, A.; Querol, X.; Alastuey, A.

    2014-06-01

    Aerosol light scattering (σsp), backscattering (σbsp) and absorption (σap) were measured at Montsec (MSC; 42°3' N, 0°44' E, 1570 m a.s.l.), a remote high-altitude site in the western Mediterranean Basin. Mean (±SD) σsp, σbsp and σap were 18.9 ± 20.8, 2.6 ± 2.8 and 1.5 ± 1.4 Mm-1, respectively at 635 nm during the period under study (June 2011-June 2013). Mean values of single-scattering albedo (SSA, 635 nm), the scattering Ångström exponent (SAE, 450-635 nm), backscatter-to-scatter ratio (B / S, 635 nm), asymmetry parameter (g, 635 nm), black carbon mass absorption cross section (MAC, 637 nm) and PM2.5 mass scattering cross section (MSCS, 635 nm) were 0.92 ± 0.03, 1.56 ± 0.88, 0.16 ± 0.09, 0.53 ± 0.16, 10.9 ± 3.5 m2 g-1 and 2.5 ± 1.3 m2 g-1, respectively. The scattering measurements performed at MSC were in the medium/upper range of values reported by Andrews et al. (2011) for other mountaintop sites in Europe due to the frequent regional recirculation scenarios (SREG) and Saharan dust episodes (NAF) occurring mostly in spring/summer and causing the presence of polluted layers at the MSC altitude. However, the development of upslope winds and the possible presence of planetary boundary layer air at MSC altitude in summer may also have contributed to the high scattering observed. Under these summer conditions no clear diurnal cycles were observed for the measured extensive aerosol optical properties (σsp, σbsp and σap). Conversely, low σsp and σap at MSC were measured during Atlantic advections (AA) and winter regional anticyclonic episodes (WREG) typically observed during the cold season in the western Mediterranean. Therefore, a season-dependent decrease in the magnitude of aerosol extensive properties was observed when MSC was in the free troposphere, with the highest free-troposphere vs. all-data difference observed in winter and the lowest in spring/summer. The location of MSC station allowed for a reliable characterization of aerosols

  17. The Effect of Aerosol Hygroscopicity and Volatility on Aerosol Optical Properties During Southern Oxidant and Aerosol Study

    NASA Astrophysics Data System (ADS)

    Khlystov, A.; Grieshop, A. P.; Saha, P.; Subramanian, R.

    2014-12-01

    Secondary organic aerosol (SOA) from biogenic sources can influence optical properties of ambient aerosol by altering its hygroscopicity and contributing to light absorption directly via formation of brown carbon and indirectly by enhancing light absorption by black carbon ("lensing effect"). The magnitude of these effects remains highly uncertain. A set of state-of-the-art instruments was deployed at the SEARCH site near Centerville, AL during the Southern Oxidant and Aerosol Study (SOAS) campaign in summer 2013 to measure the effect of relative humidity and temperature on aerosol size distribution, composition and optical properties. Light scattering and absorption by temperature- and humidity-conditioned aerosols was measured using three photo-acoustic extinctiometers (PAX) at three wavelengths (405 nm, 532 nm, and 870 nm). The sample-conditioning system provided measurements at ambient RH, 10%RH ("dry"), 85%RH ("wet"), and 200 C ("TD"). In parallel to these measurements, a long residence time temperature-stepping thermodenuder (TD) and a variable residence time constant temperature TD in combination with three SMPS systems and an Aerosol Chemical Speciation Monitor (ACSM) were used to assess aerosol volatility and kinetics of aerosol evaporation. We will present results of the on-going analysis of the collected data set. We will show that both temperature and relative humidity have a strong effect on aerosol optical properties. SOA appears to increase aerosol light absorption by about 10%. TD measurements suggest that aerosol equilibrated fairly quickly, within 2 s. Evaporation varied substantially with ambient aerosol loading and composition and meteorology.

  18. Aerosol Absorption in the Atmosphere: Perspectives from Global Model, Ground-Based Measurements, and Field Observations

    NASA Technical Reports Server (NTRS)

    Chin, Mian; Holben, Brent; Anderson, Tad; Quinn, Patricia; Duncan, Bryan; Ginoux, Paul

    2003-01-01

    Aerosol absorption in the atmosphere poses a major uncertainty in assessing the aerosol climate effects. This uncertainty arises from the poorly quantified aerosol sources, especially black carbon emissions, and our limited knowledge of aerosol mixing state and optical properties. Here we use a global model GOCART to simulate atmospheric aerosols, including sulfate, black carbon, organic carbon, dust, and sea salt. We compare the model calculated total aerosol optical thickness, extinction, and absorption with those quantities from the ground-based sun photometer measurements from AERONET at several different wavelengths and the field observations from ACE-Asia. We will examine what are the most sensitive factors in determining the aerosol absorption, and the consequences of assessing the aerosol radiative forcing and atmospheric heating associated with those factors.

  19. Aerosol Absorption in the Atmosphere: Perspectives from Global Model, Ground-Based Measurements, and Field Observations

    NASA Technical Reports Server (NTRS)

    Chin, Mian; Dubovik, Oleg; Holben, Brent; Torres, Omar; Anderson, Tad; Quinn, Patricia; Ginoux, Paul

    2004-01-01

    Aerosol absorption in the atmosphere poses a major uncertainty in assessing the aerosol climate effects. This uncertainty arises from the poorly quantified aerosol sources, especially black carbon emissions, and our limited knowledge of aerosol mixing state and optical properties. Here we use a global model GOCART to simulate atmospheric aerosols, including sulfate, black carbon, organic carbon, dust, and sea salt. We compare the model calculated total aerosol optical thickness, extinction, and absorption with those quantities from the ground-based sun photometer measurements from AERONET, satellite retrievals from the TOMS instrument, and field observations from ACE-Asia. We will examine the most sensitive factors in determining the aerosol absorption. and the consequences of assessing the aerosol radiative forcing and atmospheric heating associated with those factors.

  20. Aerosol Absorption in the Atmosphere: Perspectives from Global Model, Ground-Based Measurements, and Field Observations

    NASA Technical Reports Server (NTRS)

    Chin, Main; Dubovik, Oleg; Holben, Brent; Anderson, Tad; Quinn, Patricia; Duncan, Bryan; Ginoux, Paul

    2004-01-01

    Aerosol absorption in the atmosphere poses a major uncertainty in assessing the aerosol climate effects. This uncertainty arises from the poorly quantified aerosol sources, especially black carbon emissions, and our limited knowledge of aerosol mixing state and optical properties. Here we use a global model GOCART to simulate atmospheric aerosols, including sulfate, black carbon, organic carbon, dust, and sea salt. We compare the model calculated total aerosol optical thickness, extinction, and absorption with those quantities from the ground-based sun photometer measurements from AERONET at several different wavelengths and the field observations from ACE-Asia. We will examine the most sensitive factors in determining the aerosol absorption, and the consequences of assessing the aerosol radiative forcing and atmospheric heating associated with those factors.

  1. Light absorption of organic aerosol from pyrolysis of corn stalk

    NASA Astrophysics Data System (ADS)

    Li, Xinghua; Chen, Yanju; Bond, Tami C.

    2016-11-01

    Organic aerosol (OA) can absorb solar radiation in the low-visible and ultra-violet wavelengths thereby modifying radiative forcing. Agricultural waste burning emits a large quantity of organic carbon in many developing countries. In this work, we improved the extraction and analysis method developed by Chen and Bond, and extended the spectral range of OC absorption. We examined light absorbing properties of primary OA from pyrolysis of corn stalk, which is a major type of agricultural wastes. Light absorption of bulk liquid extracts of OA was measured using a UV-vis recording spectrophotometer. OA can be extracted by methanol at 95%, close to full extent, and shows polar character. Light absorption of organic aerosol has strong spectral dependence (Absorption Ångström exponent = 7.7) and is not negligible at ultra-violet and low-visible regions. Higher pyrolysis temperature produced OA with higher absorption. Imaginary refractive index of organic aerosol (kOA) is 0.041 at 400 nm wavelength and 0.005 at 550 nm wavelength, respectively.

  2. Characterization of a Photoacoustic Aerosol Absorption Spectrometer for Aircraft-based Measurements

    NASA Astrophysics Data System (ADS)

    Mason, B. J.; Wagner, N. L.; Richardson, M.; Brock, C. A.; Murphy, D. M.; Adler, G.

    2015-12-01

    Atmospheric aerosol directly impacts the Earth's climate through extinction of incoming and outgoing radiation. The optical extinction is due to both scattering and absorption. In situ measurements of aerosol extinction and scattering are well established and have uncertainties less than 5%. However measurements of aerosol absorption typically have uncertainties of 20-30%. Development and characterization of more accurate and precise instrumentation for measurement of aerosol absorption will enable a deeper understand of significance and spatial distribution of black and brown carbon aerosol, the effect of atmospheric processes on aerosol optical properties, and influence of aerosol optical properties on direct radiative forcing. Here, we present a detailed characterization of a photoacoustic aerosol absorption spectrometer designed for deployment aboard research aircraft. The spectrometer operates at three colors across the visible spectrum and is calibrated in the field using ozone. The field calibration is validated in the laboratory using synthetic aerosol and simultaneous measurements of extinction and scattering. In addition, the sensitivity of the instrument is characterized under conditions typically encountered during aircraft sampling e.g. as a function of changing pressure. We will apply this instrument characterization to ambient aerosol absorption data collected during the SENEX and SEAC4RS aircraft based field campaigns.

  3. Infrared Absorption by Atmospheric Aerosols in Mexico City during MILAGRO.

    NASA Astrophysics Data System (ADS)

    Kelley, K. L.; Mangu, A.; Gaffney, J. S.; Marley, N. A.

    2007-12-01

    Past research in our group using cylindrical internal reflectance spectroscopy has indicated that aqueous aerosols could contribute to the radiative warming as greenhouse species (1,2). Although aerosol radiative effects have been known for sometime and are considered one of the major uncertainties in climate change modeling, most of the studies have focused on the forcing due to scattering and absorption of radiation in the uv- visible region (3). Infrared spectral information also allows the confirmation of key functional groups that are responsible for enhanced absorption observations from secondary organics in the uv-visible region. This work extends our efforts to evaluate the infrared absorption by aerosols, particularly organics, that are now found to be a major fraction of urban and regional aerosols in the 0.1 to 1.0 micron size range and to help identify key types of organics that can contribute to aerosol absorption. During the MILAGRO campaign, quartz filter samples were taken at 12-hour intervals from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. These samples were taken at the two super-sites, T-0 (Instituto Mexicano de Petroleo in Mexico City) and T-1 (Universidad Technologica de Tecamac, State of Mexico). The samples have been characterized for total carbon content (stable isotope mass spectroscopy) and natural radionuclide tracers, as well as for their UV-visible spectroscopic properties by using integrating sphere diffuse reflectance spectroscopy (Beckman DU with a Labsphere accessory). These same samples have been characterized in the mid and near infrared spectral ranges using diffuse reflection spectroscopy (Nicolet 6700 FTIR with a Smart Collector accessory). Aerosol samples were removed from the surfaces of the aerosol filters by using Si-Carb sampler. The samples clearly indicate the presence of carbonyl organic constituents and the spectra are quite similar to those observed for humic and fulvic acids

  4. Atmospheric aerosols: Their Optical Properties and Effects

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Measured properties of atmospheric aerosol particles are presented. These include aerosol size frequency distribution and complex retractive index. The optical properties of aerosols are computed based on the presuppositions of thermodynamic equilibrium and of Mie-theory.

  5. Aerosol Sources, Absorption, and Intercontinental Transport: Synergies among Models, Remote Sensing, and Atmospheric Measurements

    NASA Technical Reports Server (NTRS)

    Chin, Mian; Ginoux, Paul; Dubovik, Oleg; Holben, Brent; Kaufman, Yoram; chu, Allen; Anderson, Tad; Quinn, Patricia

    2003-01-01

    Aerosol climate forcing is one of the largest uncertainties in assessing the anthropogenic impact on the global climate system. This uncertainty arises from the poorly quantified aerosol sources, especially black carbon emissions, our limited knowledge of aerosol mixing state and optical properties, and the consequences of intercontinental transport of aerosols and their precursors. Here we use a global model GOCART to simulate atmospheric aerosols, including sulfate, black carbon, organic carbon, dust, and sea salt, from anthropogenic, biomass burning, and natural sources. We compare the model calculated aerosol extinction and absorption with those quantities from the ground-based sun photometer measurements from AERONET at several different wavelengths and the field observations from ACE-Asia, and model calculated total aerosol optical depth and fine mode fractions with the MODIS satellite retrieval. We will also estimate the intercontinental transport of pollution and dust aerosols from their source regions to other areas in different seasons.

  6. Aerosol Sources, Absorption, and Intercontinental Transport: Synergies Among Models, Remote Sensing, and Atmospheric Measurements

    NASA Technical Reports Server (NTRS)

    Chin, Mian; Chu, Allen; Levy, Robert; Remer, Lorraine; Kaufman, Yoram; Dubovik, Oleg; Holben, Brent; Eck, Tom; Anderson, Tad; Quinn, Patricia

    2004-01-01

    Aerosol climate forcing is one of the largest uncertainties in assessing the anthropogenic impact on the global climate system. This uncertainty arises from the poorly quantified aerosol sources, especially black carbon emissions, our limited knowledge of aerosol mixing state and optical properties, and the consequences of intercontinental transport of aerosols and their precursors. Here we use a global model GOCART to simulate atmospheric aerosols, including sulfate, black carbon, organic carbon, dust, and sea salt, from anthropogenic, .biomass burning, and natural sources. We compare the model calculated aerosol extinction and absorption with those quantities from the ground-based sun photometer measurements from AERON" at several different wavelengths and the field observations from ACE-Asia, and model calculated total aerosol optical depth and fine mode fractions with the MODIS satellite retrieval. We will also estimate the intercontinental transport of pollution and dust aerosols from their source regions to other areas in different seasons.

  7. Evaluating model parameterizations of submicron aerosol scattering and absorption with in situ data from ARCTAS 2008

    NASA Astrophysics Data System (ADS)

    Alvarado, Matthew J.; Lonsdale, Chantelle R.; Macintyre, Helen L.; Bian, Huisheng; Chin, Mian; Ridley, David A.; Heald, Colette L.; Thornhill, Kenneth L.; Anderson, Bruce E.; Cubison, Michael J.; Jimenez, Jose L.; Kondo, Yutaka; Sahu, Lokesh K.; Dibb, Jack E.; Wang, Chien

    2016-07-01

    Accurate modeling of the scattering and absorption of ultraviolet and visible radiation by aerosols is essential for accurate simulations of atmospheric chemistry and climate. Closure studies using in situ measurements of aerosol scattering and absorption can be used to evaluate and improve models of aerosol optical properties without interference from model errors in aerosol emissions, transport, chemistry, or deposition rates. Here we evaluate the ability of four externally mixed, fixed size distribution parameterizations used in global models to simulate submicron aerosol scattering and absorption at three wavelengths using in situ data gathered during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The four models are the NASA Global Modeling Initiative (GMI) Combo model, GEOS-Chem v9-02, the baseline configuration of a version of GEOS-Chem with online radiative transfer calculations (called GC-RT), and the Optical Properties of Aerosol and Clouds (OPAC v3.1) package. We also use the ARCTAS data to perform the first evaluation of the ability of the Aerosol Simulation Program (ASP v2.1) to simulate submicron aerosol scattering and absorption when in situ data on the aerosol size distribution are used, and examine the impact of different mixing rules for black carbon (BC) on the results. We find that the GMI model tends to overestimate submicron scattering and absorption at shorter wavelengths by 10-23 %, and that GMI has smaller absolute mean biases for submicron absorption than OPAC v3.1, GEOS-Chem v9-02, or GC-RT. However, the changes to the density and refractive index of BC in GC-RT improve the simulation of submicron aerosol absorption at all wavelengths relative to GEOS-Chem v9-02. Adding a variable size distribution, as in ASP v2.1, improves model performance for scattering but not for absorption, likely due to the assumption in ASP v2.1 that BC is present at a constant mass fraction

  8. Identification of key aerosol populations through their size and composition resolved spectral scattering and absorption

    NASA Astrophysics Data System (ADS)

    Costabile, F.; Barnaba, F.; Angelini, F.; Gobbi, G. P.

    2013-03-01

    Characterizing chemical and physical aerosol properties is important to understand their sources, effects, and feedback mechanisms in the atmosphere. This study proposes a scheme to classify aerosol populations based on their spectral optical properties (absorption and scattering). The scheme is obtained thanks to the outstanding set of information on particle size and composition these properties contain. The spectral variability of the aerosol single scattering albedo (dSSA), and the extinction, scattering and absorption Angstrom exponents (EAE, SAE and AAE, respectively) were observed on the basis of two-year measurements of aerosol optical properties (scattering and absorption coefficients at blue, green and red wavelengths) performed in the suburbs of Rome (Italy). Optical measurements of various aerosol types were coupled to measurements of particle number size distributions and relevant optical properties simulations (Mie theory). These latter allowed the investigation of the role of the particle size and composition in the bulk aerosol properties observed. The combination of simulations and measurements suggested a general "paradigm" built on dSSA, SAE and AAE to optically classify aerosols. The paradigm proved suitable to identify the presence of key aerosol populations, including soot, biomass burning, organics, dust and marine particles. The work highlights that (i) aerosol populations show distinctive combinations of SAE and dSSA times AAE, these variables being linked by a linear inverse relation varying with varying SSA; (ii) fine particles show EAE > 1.5, whilst EAE < 2 is found for both coarse particles and ultrafine soot-rich aerosols; (iii) fine and coarse particles both show SSA > 0.8, whilst ultrafine urban Aitken mode and soot particles show SSA < 0.8. The proposed paradigm agrees with aerosol observations performed during past major field campaigns, this indicating that relations concerning the paradigm have a general validity.

  9. Black carbon aerosol mixing state, organic aerosols and aerosol optical properties over the United Kingdom

    NASA Astrophysics Data System (ADS)

    McMeeking, G. R.; Morgan, W. T.; Flynn, M.; Highwood, E. J.; Turnbull, K.; Haywood, J.; Coe, H.

    2011-09-01

    Black carbon (BC) aerosols absorb sunlight thereby leading to a positive radiative forcing and a warming of climate and can also impact human health through their impact on the respiratory system. The state of mixing of BC with other aerosol species, particularly the degree of internal/external mixing, has been highlighted as a major uncertainty in assessing its radiative forcing and hence its climate impact, but few in situ observations of mixing state exist. We present airborne single particle soot photometer (SP2) measurements of refractory BC (rBC) mass concentrations and mixing state coupled with aerosol composition and optical properties measured in urban plumes and regional pollution over the United Kingdom. All data were obtained using instrumentation flown on the UK's BAe-146-301 large Atmospheric Research Aircraft (ARA) operated by the Facility for Airborne Atmospheric Measurements (FAAM). We measured sub-micron aerosol composition using an aerosol mass spectrometer (AMS) and used positive matrix factorization to separate hydrocarbon-like (HOA) and oxygenated organic aerosols (OOA). We found a higher number fraction of thickly coated rBC particles in air masses with large OOA relative to HOA, higher ozone-to-nitrogen oxides (NOx) ratios and large concentrations of total sub-micron aerosol mass relative to rBC mass concentrations. The more ozone- and OOA-rich air masses were associated with transport from continental Europe, while plumes from UK cities had higher HOA and NOx and fewer thickly coated rBC particles. We did not observe any significant change in the rBC mass absorption efficiency calculated from rBC mass and light absorption coefficients measured by a particle soot absorption photometer despite observing significant changes in aerosol composition and rBC mixing state. The contributions of light scattering and absorption to total extinction (quantified by the single scattering albedo; SSA) did change for different air masses, with lower SSA

  10. Volcanic Aerosol Radiative Properties

    NASA Technical Reports Server (NTRS)

    Lacis, Andrew

    2015-01-01

    Large sporadic volcanic eruptions inject large amounts of sulfur bearing gases into the stratosphere which then get photochemically converted to sulfuric acid aerosol droplets that exert a radiative cooling effect on the global climate system lasting for several years.

  11. Simulations of the Aerosol Index and the Absorption Aerosol Optical Depth and Comparisons with OMI Retrievals During ARCTAS-2008 Campaign

    NASA Technical Reports Server (NTRS)

    2010-01-01

    We have computed the Aerosol Index (AI) at 354 nm, useful for observing the presence of absorbing aerosols in the atmosphere, from aerosol simulations conducted with the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) module running online the GEOS-5 Atmospheric GCM. The model simulates five aerosol types: dust, sea salt, black carbon, organic carbon and sulfate aerosol and can be run in replay or data assimilation modes. In the assimilation mode, information's provided by the space-based MODIS and MISR sensors constrains the model aerosol state. Aerosol optical properties are then derived from the simulated mass concentration and the Al is determined at the OMI footprint using the radiative transfer code VLIDORT. In parallel, model derived Absorption Aerosol Optical Depth (AAOD) is compared with OMI retrievals. We have focused our study during ARCTAS (June - July 2008), a period with a good sampling of dust and biomass burning events. Our ultimate goal is to use OMI measurements as independent validation for our MODIS/MISR assimilation. Towards this goal we document the limitation of OMI aerosol absorption measurements on a global scale, in particular sensitivity to aerosol vertical profile and cloud contamination effects, deriving the appropriate averaging kernels. More specifically, model simulated (full) column integrated AAOD is compared with model derived Al, this way identifying those regions and conditions under which OMI cannot detect absorbing aerosols. Making use of ATrain cloud measurements from MODIS, C1oudSat and CALIPSO we also investigate the global impact on clouds on OMI derived Al, and the extent to which GEOS-5 clouds can offer a first order representation of these effects.

  12. Method and apparatus for aerosol particle absorption spectroscopy

    DOEpatents

    Campillo, Anthony J.; Lin, Horn-Bond

    1983-11-15

    A method and apparatus for determining the absorption spectra, and other properties, of aerosol particles. A heating beam source provides a beam of electromagnetic energy which is scanned through the region of the spectrum which is of interest. Particles exposed to the heating beam which have absorption bands within the band width of the heating beam absorb energy from the beam. The particles are also illuminated by light of a wave length such that the light is scattered by the particles. The absorption spectra of the particles can thus be determined from an analysis of the scattered light since the absorption of energy by the particles will affect the way the light is scattered. Preferably the heating beam is modulated to simplify the analysis of the scattered light. In one embodiment the heating beam is intensity modulated so that the scattered light will also be intensity modulated when the particles absorb energy. In another embodiment the heating beam passes through an interferometer and the scattered light reflects the Fourier Transform of the absorption spectra.

  13. Retrieval of Spectral Aerosol Optical Properties and Their Relationship to Aerosol Chemistry During ARCTAS

    NASA Astrophysics Data System (ADS)

    Corr, C. A.; Hall, S. R.; Ullmann, K.; Shetter, R.; Anderson, B. E.; Beyersdorf, A. J.; Thornhill, K. L.; Cubison, M.; Jimenez, J. L.; Dibb, J. E.

    2010-12-01

    Aerosols are known to both absorb and scatter radiation at UV wavelengths with the degree of absorption/scattering largely dependent on aerosol chemistry. The interactions of aerosols with the UV radiation field were examined during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS). Analysis focused on two case studies; one flight from the first phase of ARCTAS over Alaska and the Arctic ocean (Flight 10, April 2008) and the other from the second phase over northern Canada (Flight 17, June 2008). These flights were chosen based on availability of aircraft profiles through pollution layers and biomass burning smoke plumes with high loadings of organic aerosol during flight. Aerosol single scattering albedo (ω) was retrieved at near-UV (350-400nm) wavelengths at 1nm resolution from spectral actinic flux data collected aboard the NASA DC-8 aircraft during ARCTAS using two CCD Actinic Flux Spectroradiometers. Retrievals were performed using the Tropospheric Ultraviolet Model version 4.6 (TUV 4.6). Inputs of trace gas (e.g., NO2, SO2) concentrations, aerosol optical depth, location, time, pressure, etc. required by TUV were determined from ancillary aircraft measurements made from the DC-8. Values of ω were subsequently used to determine absorption optical depth (τabs) for each of the examined flights. Retrieval and calculation results were compared to aerosol optical properties in the visible (calculated from measurements of absorption and scattering aboard the DC-8) and the spectral dependencies characterized. Spectral ω and τabs were compared with aerosol chemistry data collected by an Aerosol Mass Spectrometer (AMS) to provide insight into the role of aerosol composition on absorption in the UV wavelength range. In particular, spectral dependencies were compared to the oxidation state of the organic aerosol (determined from AMS data) to examine the impact of aerosol processing/aging on spectral ω and τabs.

  14. In Situ Measurements of Aerosol Mass Concentration and Spectral Absorption in Xianghe, SE of Beijing, China

    NASA Astrophysics Data System (ADS)

    Chaudhry, Z.; Martins, V.; Li, Z.

    2005-12-01

    China's rapid industrialization over the last few decades has affected air quality in many regions of China, and even the regional climate. As a part of the EAST-AIRE (East Asian Study of Tropospheric Aerosols: an International Regional Experiment) study, Nuclepore filters were collected in two size ranges (PM10 and PM2.5) at 12 hour intervals since January 2005 at Xianghe, about 70 km southeast of Beijing. Each filter was analyzed for mass concentration, aerosol scattering and absorption efficiencies. Mass concentrations during the winter months (January-March) ranged from 9 to 459 μg/m3 in the coarse mode with an average concentration of 122 μg/m3, and from 11 to 203 μg/m3 in the fine mode with an average concentration of 45 μg/m3. While some of the extreme values are likely linked to local emissions, regional air pollution episodes also played important roles. Absorption efficiency measurements at 550 nm show very high values compared to measurements performed in the United States during the CLAMS experiment. The spectral mass absorption efficiency was measured from 350 to 2500 nm and shows large differences between the absorption properties of soil dust, black carbon, and organic aerosols. The strong spectral differences observed can be related to differences in refractive indices from the several collected species and particle size effects. The absorption properties from aerosols measured in China show large absorption efficiencies, compared to aerosols measured in the US, possibly linked to different technology practices used in these countries. For organic plus black carbon aerosols, where the refractive index seems to be relatively constant, the absorption efficiency spectral dependence for fine mode aerosols falls between 1/λ and 1/λ2. The coarse mode absorption shows much less spectral dependence.

  15. Aerosol absorption measurement at SWIR with water vapor interference using a differential photoacoustic spectrometer.

    PubMed

    Zhu, Wenyue; Liu, Qiang; Wu, Yi

    2015-09-01

    Atmospheric aerosol plays an important role in atmospheric radiation balance through absorbing and scattering the solar radiation, which changes local weather and global climate. Accurate measurement is highly requested to estimate the radiative effects and climate effects of atmospheric aerosol. Photoacoustic spectroscopy (PAS) technique, which observes the aerosols on their natural suspended state and is insensitive to light scattering, is commonly recognized as one of the best candidates to measure the optical absorption coefficient (OAC) of aerosols. In the present work, a method of measuring aerosol OAC at the wavelength where could also be absorbed by water vapor was proposed and corresponding measurements of the absorption properties of the atmospheric aerosol at the short wave infrared (SWIR, 1342 nm) wavelength were carried out. The spectrometer was made up of two high performance homemade photoacoustic cells. To improve the sensitivity, several methods were presented to control the noise derived from gas flow and vibration from the sampling pump. Calibration of the OAC and properties of the system were also studied in detail. Using the established PAS instrument, measurement of the optical absorption properties of the atmospheric aerosol were carried out in laboratory and field environment.

  16. Aerosol absorption measurement at SWIR with water vapor interference using a differential photoacoustic spectrometer.

    PubMed

    Zhu, Wenyue; Liu, Qiang; Wu, Yi

    2015-09-01

    Atmospheric aerosol plays an important role in atmospheric radiation balance through absorbing and scattering the solar radiation, which changes local weather and global climate. Accurate measurement is highly requested to estimate the radiative effects and climate effects of atmospheric aerosol. Photoacoustic spectroscopy (PAS) technique, which observes the aerosols on their natural suspended state and is insensitive to light scattering, is commonly recognized as one of the best candidates to measure the optical absorption coefficient (OAC) of aerosols. In the present work, a method of measuring aerosol OAC at the wavelength where could also be absorbed by water vapor was proposed and corresponding measurements of the absorption properties of the atmospheric aerosol at the short wave infrared (SWIR, 1342 nm) wavelength were carried out. The spectrometer was made up of two high performance homemade photoacoustic cells. To improve the sensitivity, several methods were presented to control the noise derived from gas flow and vibration from the sampling pump. Calibration of the OAC and properties of the system were also studied in detail. Using the established PAS instrument, measurement of the optical absorption properties of the atmospheric aerosol were carried out in laboratory and field environment. PMID:26368414

  17. Measurements and Modeling of Aerosol Absorption and Single Scattering Albedo at Ambient Relative Hum

    NASA Technical Reports Server (NTRS)

    Redemann, J.; Russell, P. B.; Hamill, P.

    2000-01-01

    Uncertainties in the aerosol single scattering albedo have been identified to be an important source of errors in current large-scale model estimates of the direct aerosol radiative forcing of climate. A number of investigators have obtained estimates of the single scattering albedo from a variety of remote sensing and in situ measurements during aerosol field experiments. During the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX, 1996) for example, estimates of the aerosol single scattering albedo were obtained (1) as a best-fit parameter in comparing radiative flux changes measured by airborne pyranometer to those computed from independently measured aerosol properties; (2) from estimates of the aerosol complex index of refraction derived using a combination of airborne sunphotometer, lidar backscatter and in situ size distribution measurements; and (3) from airborne measurements of aerosol scattering and absorption using nephelometers and absorption photometers. In this paper, we briefly compare the results of the latter two methods for two TARFOX case studies, since those techniques provide height-resolved information about the aerosol single scattering albedo. Estimates of the aerosol single scattering albedo from nephelometer and absorption photometer measurements require knowledge of the scattering and absorption humidification (i.e., the increase in these properties in response to an increase in ambient relative humidity), since both measurements are usually carried out at a relative humidity different from the ambient atmosphere. In principle, the scattering humidification factor can be measured, but there is currently no technique widely available to measure the absorption of an aerosol sample as a function of relative humidity. Frequently, for lack of better knowledge, the absorption humidification is assumed to be unity (meaning that there is no change in aerosol absorption due to an increase in ambient relative humidity). This

  18. Does atmospheric aging of biogenic SOA increase aerosol absorption and brown carbon?

    NASA Astrophysics Data System (ADS)

    Rudich, Yinon

    2014-05-01

    The optical properties of organic aerosols are important in determining their radiative forcing and, subsequently, their impact on climate. Primary or secondary organic aerosols (SOA) from natural and anthropogenic emissions age via photochemical reactions of OH, NO3, and O3. Atmospheric aging of aerosols changes their chemical, physical, and optical properties. Of special interest is the possible formation of absorbing organic species or "brown carbon", which can lead to absorption and heating in the atmosphere, with important consequences to climate and air quality. In this talk we will discuss possible formation pathways of brown carbon by aging of SOA, and its potential effect on radiative forcing. We employed a new broadband aerosol spectrometer that retrieves aerosol optical properties between 360 and 420 nm to probe the aging of biogenic and anthropogenic SOA in a flowtube and photochemical smog chamber. We will discuss the effect of photochemical aging on the optical properties of SOA that form from the ozonolysis of biogenic and anthropogenic VOCs, and subsequent reactions with ammonia with special emphasis on the change in their absorption. Nitration reactions of polyaromatic hydrocarbons that lead to increased absorption will also be presented. Using the wavelength-dependent modified forcing equation we will provide estimates of the radiative impact of the aged biogenic SOA. Our calculation shows that the integrated radiative forcing suggest that the observed changes in refractive index due to photochemical ageing by NH3 reactions can lead to enhanced cooling by the aged aerosol.

  19. Size segregated light absorption coefficient of the atmospheric aerosol

    NASA Astrophysics Data System (ADS)

    Horvath, H.

    The light absorption coefficient of atmospheric aerosols in the visible can be determined by depositing the particles on a filter and measuring its "transmission" in a special optical arrangement. With an impactor with rotating impaction plates producing a homogeneous deposit, it is possible to extend this technique to size segregated aerosol samples. A simultaneous determination of the mass size distribution is possible. Test measurements with black carbon aerosol have shown the feasibility of this method. Samples of the atmospheric aerosol have been taken in and near Vienna, in Naples and near Bologna. The light absorption of the aerosol is always highest for particle diameters between 0.1 and 0.2 μm. Only in the humid environment of the Po valley it had a slightly larger peak size, whereas the size of the nonabsorbing particles increased considerably. The light absorption of the atmospheric aerosol is always higher in an urban environment. 'The mass absorption coefficient of the aerosol at all four locations was very similar, and completely different from values which could be. expected using effective refractive indices which are frequently used in models. Using the data measured in this work two alternate models for the effective refractive index and black carbon content of the aerosol are suggested: (a) a size-dependent refractive index, where the imaginary part varies from -0.25 for particles smaller than 30 nm to - 0.003 for particles larger than 2 μm; this could especially be applied if an internal mixing of the aerosol is to be expected, or (2) a size-dependent fraction of elemental carbon in the case of external mixing with 43% of carbon particles for sizes below 30 nm decreasing to 10% for sizes up to 0.4 μm.

  20. Impacts of nonrefractory material on light absorption by aerosols emitted from biomass burning

    NASA Astrophysics Data System (ADS)

    McMeeking, G. R.; Fortner, E.; Onasch, T. B.; Taylor, J. W.; Flynn, M.; Coe, H.; Kreidenweis, S. M.

    2014-11-01

    We present laboratory measurements of biomass-burning aerosol light-scattering and light absorption coefficients at 405, 532, and 781 nm and investigate their relationship with aerosol composition and fuel type. Aerosol composition measurements included nonrefractory components measured by a high-resolution aerosol mass spectrometer (AMS), composition of refractory black carbon-containing particles by a soot particle aerosol mass spectrometer (SP-AMS), and refractory black carbon measured by a single-particle soot photometer (SP2). All measurements were performed downstream of a thermal denuder system to probe the effects of nonrefractory material on observed optical properties. The fires studied emitted aerosol with a wide range of optical properties with some producing more strongly light-absorbing particles (single-scattering albedo or SSA at 781 nm = 0.4) with a weak wavelength dependence of absorption (absorption Ångström exponent or AAE = 1-2) and others producing weakly light-absorbing particles (SSA at 781 nm ~1) with strong wavelength dependence of absorption (AAE ~7). Removal of nonrefractory material from the particles by the thermal denuder system led to substantial (20-80%) decreases in light absorption coefficients, particularly at shorter wavelengths, reflecting the removal of light-absorbing material that had enhanced black carbon absorption in internally mixed untreated samples. Observed enhancements of absorption by all mechanisms were at least factors of 1.2-1.5 at 532 nm and 781 nm as determined from the heated samples. A mass absorption cross-section-based approach indicated larger enhancements, particularly at shorter wavelengths.

  1. Contribution of Brown Carbon to Total Aerosol Absorption in Indo-Gangetic Plain

    NASA Astrophysics Data System (ADS)

    Tripathi, S. N.; Moosakutty, S. P.; Bergin, M.; Vreeland, H. P.

    2015-12-01

    Carbonaceous aerosols play an important role in earth's radiative balance by absorbing and scattering light. We report physical and optical properties of carbonaceous aerosols from Indo-Gangetic Plain (IGP) for 60 days during 2014-15 winter season. Mass concentration and size distribution of black carbon (BC) and organic carbon (OC) were measured in real time using Single Particle Soot Photometer (SP2) and High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) respectively. Optical properties of aerosols at atmospheric and denuded (heated at 300 ˚C) conditions were also measured using 3 wavelength Photo Acoustic Soot Spectrometer (PASS 3). Analysis shows large scale carbonaceous aerosol loading during winter season in IGP. Multiple biomass burning events combined with trash burning contributed to this high loading along with very low boundary layer height. An inter-comparison shows that Aethalometer over estimates BC by a factor of 3 when compared with that of SP 2 measurement. Enhancement in absorption (Eabs) defined as the ratio of atmospheric absorption to denuded absorption shows presence of absorbing organics known as brown carbon (BrC). Optical closure performed between denuded aerosol absorption measured by PASS 3 and Mie theory derived absorption using SP 2 BC size distribution showed a difference of only 30 % at 781 nm. This difference might be due to the non-spherical shape and presence of residual coating on BC. Refractive index of BrC at 405 and 532 nm were derived using optical closure method for the entire sampling period. Overall results indicates that the impact of BrC on optical absorption is significant in areas dominated by biomass burning such as IGP and such effects needs to be considered in global aerosol modelling studies.

  2. Light Absorption of Biogenic Aerosol Particles in Amazonia

    NASA Astrophysics Data System (ADS)

    Holanda, B. A.; Artaxo, P.; Ferreira De Brito, J.; Barbosa, H. M.; Andreae, M. O.; Saturno, J.; Pöhlker, C.; Holben, B. N.; Schafer, J.

    2014-12-01

    Aerosol absorption is a key issue in proper calculation of aerosol radiative forcing. Especially in the tropics with the dominance of natural biogenic aerosol and brown carbon, the so called anomalous absorption is of particular interest. A special experiment was designed to study the wavelength dependence of aerosol absorption for PM2.5 as well as for PM10 particles in the wet season in Central Amazonia. Aerosol analysis occurred from May to August 2014, in the ZF2 ecological reservation, situated at about 55 km North of Manaus in very pristine conditions Two 7 wavelengths AE33 Aethalometers were deployed measuring in parallel, but with a PM2.5 and PM10 inlets. Two MAAP (Multiangle Aerosol Absorption Photometer) were operated in parallel with the AE33 exactly at the same PM2.5 and PM10 inlets. Organic and elemental carbon was analyzed using collection with quartz filters and analysis using a Sunset OC/EC analyzer. Aerosol light scattering for 3 wavelengths was measured using Air Photon and TSI Nephelometers. Aerosol size distribution was measured with one TSI SMPS and a GRIMM OPC to have the size range from 10 nm to 10 micrometers. Particles were measured under dry conditions using diffusion dryers. Aerosol optical depth and absorption was also measured with an AERONET sunphotometer operated close to the site. As the experiment was run in the wet season, very low equivalent black carbon (EBC) were measured, with average concentrations around 50 ng/m³ during May, increasing to 130 ng/m³ in June and July. The measurements adjusted for similar wavelengths shows excellent agreement between the MAAP and AE33 for both inlets (PM2.5 and PM10). It was not possible statistically infer absorption from the coarse mode biogenic particles, since the absorption was completely dominated by fine mode particles. AERONET measurements shows very low values of AOD, at 0.17 at 500 nm and 0.13 at 870 nm, with very low absorption AOD values at 0.00086 at 676 nm and 0.0068 at 872 nm

  3. Characterization and intercomparison of aerosol absorption photometers: result of two intercomparison workshops

    NASA Astrophysics Data System (ADS)

    Müller, T.; Henzing, J. S.; de Leeuw, G.; Wiedensohler, A.; Alastuey, A.; Angelov, H.; Bizjak, M.; Collaud Coen, M.; Engström, J. E.; Gruening, C.; Hillamo, R.; Hoffer, A.; Imre, K.; Ivanow, P.; Jennings, G.; Sun, J. Y.; Kalivitis, N.; Karlsson, H.; Komppula, M.; Laj, P.; Li, S.-M.; Lunder, C.; Marinoni, A.; Martins Dos Santos, S.; Moerman, M.; Nowak, A.; Ogren, J. A.; Petzold, A.; Pichon, J. M.; Rodriquez, S.; Sharma, S.; Sheridan, P. J.; Teinilä, K.; Tuch, T.; Viana, M.; Virkkula, A.; Weingartner, E.; Wilhelm, R.; Wang, Y. Q.

    2010-04-01

    Absorption photometers for real time application have been available since the 1980s, but the use of filter-based instruments to derive information on aerosol properties (absorption coefficient and black carbon, BC) is still a matter of debate. Several workshops have been conducted to investigate the performance of individual instruments over the intervening years. Two workshops with large sets of aerosol absorption photometers were conducted in 2005 and 2007. The data from these instruments were corrected using existing methods before further analysis. The inter-comparison shows a large variation between the responses to absorbing aerosol particles for different types of instruments. The unit to unit variability between instruments can be up to 30% for Particle Soot Absorption Photometers (PSAPs) and Aethalometers. Multi Angle Absorption Photometers (MAAPs) showed a variability of less than 5%. Reasons for the high variability were identified to be variations in sample flow and spot size. It was observed that different flow rates influence system performance with respect to response to absorption and instrumental noise. Measurements with non absorbing particles showed that the current corrections of a cross sensitivity to particle scattering are not sufficient. Remaining cross sensitivities were found to be a function of the total particle load on the filter. The large variation between the response to absorbing aerosol particles for different types of instruments indicates that current correction functions for absorption photometers are not adequate.

  4. Characterization and intercomparison of aerosol absorption photometers: result of two intercomparison workshops

    NASA Astrophysics Data System (ADS)

    Müller, T.; Henzing, J. S.; de Leeuw, G.; Wiedensohler, A.; Alastuey, A.; Angelov, H.; Bizjak, M.; Collaud Coen, M.; Engström, J. E.; Gruening, C.; Hillamo, R.; Hoffer, A.; Imre, K.; Ivanow, P.; Jennings, G.; Sun, J. Y.; Kalivitis, N.; Karlsson, H.; Komppula, M.; Laj, P.; Li, S.-M.; Lunder, C.; Marinoni, A.; Martins Dos Santos, S.; Moerman, M.; Nowak, A.; Ogren, J. A.; Petzold, A.; Pichon, J. M.; Rodriquez, S.; Sharma, S.; Sheridan, P. J.; Teinilä, K.; Tuch, T.; Viana, M.; Virkkula, A.; Weingartner, E.; Wilhelm, R.; Wang, Y. Q.

    2011-02-01

    Absorption photometers for real time application have been available since the 1980s, but the use of filter-based instruments to derive information on aerosol properties (absorption coefficient and black carbon, BC) is still a matter of debate. Several workshops have been conducted to investigate the performance of individual instruments over the intervening years. Two workshops with large sets of aerosol absorption photometers were conducted in 2005 and 2007. The data from these instruments were corrected using existing methods before further analysis. The inter-comparison shows a large variation between the responses to absorbing aerosol particles for different types of instruments. The unit to unit variability between instruments can be up to 30% for Particle Soot Absorption Photometers (PSAPs) and Aethalometers. Multi Angle Absorption Photometers (MAAPs) showed a variability of less than 5%. Reasons for the high variability were identified to be variations in sample flow and spot size. It was observed that different flow rates influence system performance with respect to response to absorption and instrumental noise. Measurements with non absorbing particles showed that the current corrections of a cross sensitivity to particle scattering are not sufficient. Remaining cross sensitivities were found to be a function of the total particle load on the filter. The large variation between the response to absorbing aerosol particles for different types of instruments indicates that current correction functions for absorption photometers are not adequate.

  5. Influence of semi-volatile aerosol on physical and optical properties of aerosol in Kathmandu valley

    NASA Astrophysics Data System (ADS)

    Shrestha, Sujan; Praveen, Ps; Adhikary, Bhupesh; Shrestha, Kundan; Panday, Arnico

    2016-04-01

    A field study was conducted in the urban atmosphere of Kathmandu valley to study the influence of the semi-volatile aerosol fraction on physical and optical properties of aerosols. The study was carried out during the 2015 pre-monsoon period. Experimental setup consisted of air from an ambient air inlet being split to two sets of identical sampling instruments. The first instrument received the ambient sample directly, while the second instrument received the air sample through a thermodenuder (TDD). Four sets of experiments were conducted to understand aerosol number, size distribution, scattering and absorption properties using Condensation Particle Counter (CPC), Scanning Mobility Particle Sizer (SMPS), Aethalometer (AE33) and Nephelometer. The influence of semi-volatile aerosols was calculated from the fraction of particles evaporated in the TDD at set temparetures: room temperature, 50°C, 100°C, 150°C, 200°C, 250°C and 300°C. Results show that, with increasing temperature, the evaporated fraction of semi-volatile aerosol also increased. At room temperature the fraction of semi-volatile aerosols was 12% while at 300°C it was as high as to 49%. Aerosol size distribution analysis shows that with an increase in TDD temperature from 50°C to 300°C, peak mobility diameter of particles shifted from around 60nm to 40nm. However we found little change in effective diameter of aerosol size distribution with increase in set TDD temperature. The change in size of aerosols due to loss of semi-volatile component has a stronger influence (~70%) in higher size bins when compared to at lower size bins (~20%). Studies using the AE33 showed that absorption by black carbon (BC) is amplified due to influence of semi-volatile aerosols by upto 37% at 880nm wavelength. Similarly nephelometer measurements showed that upto 71% of total scattering was found to be contributed by semi-volatile aerosol fraction. The scattering Angstrom Exponent (SAE) of semi-volatile aerosol

  6. Aerosol Forcing of Climate Change and Anomalous Atmospheric Absorption

    NASA Technical Reports Server (NTRS)

    Hansen, James E.

    2000-01-01

    The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change, Anthropogenic greenhouse gases (GHGs), which are well-measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming. We will focus on the role of aerosols as a climate forcing mechanism and the contribution that aerosols might make to the so-called "anomalous" atmospheric absorption that has been inferred from some atmospheric measurements.

  7. Aerosol Forcing of Climate Change and "Anomalous" Atmospheric Absorption

    NASA Technical Reports Server (NTRS)

    Hansen, James E.

    1999-01-01

    The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change. Anthropogenic greenhouse gases (GHGs), which are well-measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming. We will focus on the role of aerosols as a climate forcing mechanism and the contribution that aerosols might make to the so- called "anomalous" atmospheric absorption that has been inferred from some atmospheric measurements.

  8. Equilibrium absorptive partitioning theory between multiple aerosol particle modes

    NASA Astrophysics Data System (ADS)

    Crooks, Matthew; Connolly, Paul; Topping, David; McFiggans, Gordon

    2016-10-01

    An existing equilibrium absorptive partitioning model for calculating the equilibrium gas and particle concentrations of multiple semi-volatile organics within a bulk aerosol is extended to allow for multiple involatile aerosol modes of different sizes and chemical compositions. In the bulk aerosol problem, the partitioning coefficient determines the fraction of the total concentration of semi-volatile material that is in the condensed phase of the aerosol. This work modifies this definition for multiple polydisperse aerosol modes to account for multiple condensed concentrations, one for each semi-volatile on each involatile aerosol mode. The pivotal assumption in this work is that each aerosol mode contains an involatile constituent, thus overcoming the potential problem of smaller particles evaporating completely and then condensing on the larger particles to create a monodisperse aerosol at equilibrium. A parameterisation is proposed in which the coupled non-linear system of equations is approximated by a simpler set of equations obtained by setting the organic mole fraction in the partitioning coefficient to be the same across all modes. By perturbing the condensed masses about this approximate solution a correction term is derived that accounts for many of the removed complexities. This method offers a greatly increased efficiency in calculating the solution without significant loss in accuracy, thus making it suitable for inclusion in large-scale models.

  9. Using OMI Observations to Measure Aerosol Absorption of Biomass Burning Aerosols Above Clouds

    NASA Technical Reports Server (NTRS)

    Torres, Omar; Bhartia, P. K.; Jethva, Hiren

    2011-01-01

    The presence of absorbing aerosol layers above clouds is unambiguously detected by the TOMS/OMI UV Aerosol Index (AI) that uses satellite observations at two near-UV channels. A sensitivity study using radiative transfer calculations shows that the AI signal of resulting from the presence of aerosols above clouds is mainly driven by the aerosol absorption optical depth and the optical depth of the underlying cloud. Based on these results, an inversion algorithm has been developed to retrieve the aerosol optical depth (AOD) of aerosol layers above clouds. In this presentation we will discuss the sensitivity analysis, describe the retrieval approach, and present results of applications of the retrieval method to OMI observations over the South Atlantic Ocean. Preliminary error analyses, to be discussed, indicate that the AOD can be underestimated (up to -30%) or overestimated (up to 60%) depending on algorithmic assumptions.

  10. Influence of Brown Carbon Aerosols on Absorption Enhancement and Radiative Forcing

    NASA Astrophysics Data System (ADS)

    Shamjad, Puthukkadan; Nand Tripathi, Sachchida; Kant Pathak, Ravi; Hallquist, Mattias

    2015-04-01

    This study presents aerosol mass and optical properties measured during winter-spring months (February-March) of two consecutive years (2013-2014) from Kanpur, India located inside Gangetic Plain. Spectral absorption and scattering coefficients (405, 532 and 781 nm) of both atmospheric and denuded (at 300° C) is measured using a 3 wavelength Photo Acoustic Soot Spectrometer (PASS 3). Ratio between the atmospheric and denuded absorption is reported as enhancement in absorption (Eabs). Eabs values shows presence of large quantities of Brown Carbon (BrC) aerosols in the location. Diurnal trend of Eabs shows similar patterns at 405 and 532 nm. But at 781 nm Eabs values increased during day time (10:00 to 18:00) while that 405 and 532 nm decreased. Positive Matrix Analysis (PMF) of organic aerosols measured using HR-ToF-AMS shows factors with different trends with total absorption. Semi-volatile factor (SV-OOA) show no correlation with absorption but other factors such as Low-volatile (LV-OOA), Hydrocarbon (HOA) and Biomass burning (BBOA) organic aerosols shows a positive trend. All factors shows good correlation with scattering coefficient. Also a strong dependence of absorption is observed at 405 and 532 nm and a weak dependence at 781 nm is observed during regression analysis with factors and mass loading. We also present direct radiative forcing (DRF) calculated from measured optical properties due to total aerosol loading and only due to BrC. Total and BrC aerosol DRF shows cooling trends at top of atmosphere (TOA) and surface and warming trend in atmosphere. Days with biomass burning events shows increase in magnitude of DRF at atmosphere and surface up to 30 % corresponding to clear days. TOA forcing during biomass burning days shows increase in magnitude indicating change from negative to less negative.

  11. Multi-wavelength aerosol light absorption measurements in the Amazon rainforest

    NASA Astrophysics Data System (ADS)

    Saturno, Jorge; Chi, Xuguang; Pöhlker, Christopher; Morán, Daniel; Ditas, Florian; Massabò, Dario; Prati, Paolo; Rizzo, Luciana; Artaxo, Paulo; Andreae, Meinrat

    2015-04-01

    The most important light-absorbing aerosol is black carbon (BC), which is emitted by incomplete combustion of fossil fuels and biomass. BC is considered the second anthropogenic contributor to global warming. Beyond BC, other aerosols like some organics, dust, and primary biological aerosol particles are able to absorb radiation. In contrast to BC, the light absorption coefficient of these aerosols is wavelength dependent. Therefore, multi-wavelength measurements become important in environments where BC is not the predominant light-absorbing aerosol like in the Amazon. The Amazon Tall Tower Observatory (ATTO) site is located in the remote Amazon rainforest, one of the most pristine continental sites in the world during the wet season. In the dry season, winds coming from the southern hemisphere are loaded with biomass burning aerosol particles originated by farming-related deforestation. BC and aerosol number concentration data from the last two years indicate this is the most polluted period. Two different techniques have been implemented to measure the light absorption at different wavelengths; one of them is the 7-wavelengths Aethalometer, model AE30, an instrument that measures the light attenuation on a filter substrate and requires multiple scattering and filter-loading corrections to retrieve the light absorption coefficient. The other method is an offline technique, the Multi-Wavelength Absorbance Analysis (MWAA), which is able to measure reflectance and absorbance by aerosols collected on a filter and, by means of a radiative model, can retrieve the light absorption coefficient. Filters collected during May-September 2014, comprehending wet-to-dry transition and most of the dry season, were analyzed. The results indicate that the Absorption Ångström Exponent (AAE), a parameter that is directly proportional to the wavelength dependence of the aerosol light absorption, is close to 1.0 during the transition period and slightly decreases in the beginning of

  12. Direct Measurement of Aerosol Absorption Using Photothermal Interferometry

    NASA Astrophysics Data System (ADS)

    Sedlacek, A. J.; Lee, J. A.

    2007-12-01

    Efforts to bound the contribution of light absorption in aerosol radiative forcing is still very much an active area of research in large part because aerosol extinction is dominated by light scattering. In response to this and other technical issues, the aerosol community has actively pursued the development of new instruments to measure aerosol absorption (e.g., photoacoustic spectroscopy (PAS) and multi-angle absorption photometer (MAAP)). In this poster, we introduce the technique of photothermal interferometry (PTI), which combines the direct measurement capabilities of photothermal spectroscopy (PTS) with high-sensitivity detection of the localized heating brought about by the PT process through interferometry. At its most fundamental level, the PTI technique measures the optical pathlength change that one arm of an interferometer (referred to as the 'probe' arm) experiences relative to the other arm of the interferometer (called the 'reference' arm). When the two arms are recombined at a beamsplitter, an interference pattern is created. If the optical pathlength in one arm of the interferometer changes, a commensurate shift in the interference pattern will take place. For the specific application of measuring light absorption, the heating of air surrounding the light- absorbing aerosol following laser illumination induces the optical pathlength change. This localized heating creates a refractive index gradient causing the probe arm of the interferometer to take a slightly different optical pathlength relative to the unperturbed reference arm. This effect is analogous to solar heating of a road causing mirages. As discussed above, this altered optical pathlength results in a shift in the interference pattern that is then detected as a change in the signal intensity by a single element detector. The current optical arrangement utilizes a folded Jamin interferometer design (Sedlacek, 2006) that provides a platform that is robust with respect to sensitivity

  13. Spectral Absorption of Solar Radiation by Aerosols during ACE-Asia

    NASA Technical Reports Server (NTRS)

    Bergstrom, R. W.; Pilewskie, P.; Pommier, J.; Rabbette, M.; Russell, P. B.; Schmid, B.; Redermann, J.; Higurashi, A.; Nakajima, T.; Quinn, P. K.

    2004-01-01

    As part of the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia), the upward and downward spectral solar radiant fluxes were measured with the Spectral Solar Flux Radiometer (SSFR), and the aerosol optical depth was measured with the Ames Airborne Tracking Sunphotometer (AATS-14) aboard the Center for INterdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. IN this paper, we examine the data obtained for two cases: a moderately thick aerosol layer, 12 April, and a relatively thin aerosol case, 16 April 2001. ON both days, the Twin Otter flew vertical profiles in the Korean Strait southeast of Gosan Island. For both days we determine the aerosol spectral absorption of the layer and estimate the spectral aerosol absorption optical depth and single-scattering albedo. The results for 12 April show that the single-scattering albedo increases with wavelength from 0.8 at 400 nm to 0.95 at 900 nm and remains essentially constant from 950 to 1700 nm. On 16 April the amount of aerosol absorption was very low; however, the aerosol single-scattering albedo appears to decrease slightly with wavelength in the visible region. We interpret these results in light of the two absorbing aerosol species observed during the ACE-asia study: mineral dust and black carbon. The results for 12 April are indicative of a mineral dust-black carbon mixture. The 16 April results are possibly caused by black carbon mixed with nonabsorbing pollution aerosols. For the 12 April case we attempt to estimate the relative contributions of the black carbon particles and the mineral dust particles. We compare our results with other estimates of the aerosol properties from a Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) satellite analysis and aerosol measurements made aboard the Twin Otter, aboard the National Oceanic and Atmospheric Administration Ronald H Brown ship, and at ground sites in Gosan and Japan. The results indicate a relatively complicated aerosol

  14. A wide spectral range photoacoustic aerosol absorption spectrometer.

    PubMed

    Haisch, C; Menzenbach, P; Bladt, H; Niessner, R

    2012-11-01

    A photoacoustic spectrometer for the measurement of aerosol absorption spectra, based on the excitation of a pulsed nanosecond optical parametrical oscillator (OPO), will be introduced. This spectrometer is working at ambient pressure and can be used to detect and characterize different classes of aerosols. The spectrometer features a spectral range of 410 to 2500 nm and a sensitivity of 2.5 × 10(-7) m(-1) at 550 nm. A full characterization of the system in the visible spectral range is demonstrated, and the potential of the system for near IR measurement is discussed. In the example of different kinds of soot particles, the performance of the spectrometer was assessed. As we demonstrate, it is possible to determine a specific optical absorption per particle by a combination of the new spectrometer with an aerosol particle counter. PMID:23035870

  15. A wide spectral range photoacoustic aerosol absorption spectrometer.

    PubMed

    Haisch, C; Menzenbach, P; Bladt, H; Niessner, R

    2012-11-01

    A photoacoustic spectrometer for the measurement of aerosol absorption spectra, based on the excitation of a pulsed nanosecond optical parametrical oscillator (OPO), will be introduced. This spectrometer is working at ambient pressure and can be used to detect and characterize different classes of aerosols. The spectrometer features a spectral range of 410 to 2500 nm and a sensitivity of 2.5 × 10(-7) m(-1) at 550 nm. A full characterization of the system in the visible spectral range is demonstrated, and the potential of the system for near IR measurement is discussed. In the example of different kinds of soot particles, the performance of the spectrometer was assessed. As we demonstrate, it is possible to determine a specific optical absorption per particle by a combination of the new spectrometer with an aerosol particle counter.

  16. Application of AERONET Single Scattering Albedo and Absorption Angstrom Exponent to Classify Dominant Aerosol Types during DRAGON Campaigns

    NASA Astrophysics Data System (ADS)

    Giles, D. M.; Holben, B. N.; Eck, T. F.; Schafer, J.; Crawford, J. H.; Kim, J.; Sano, I.; Liew, S.; Salinas Cortijo, S. V.; Chew, B. N.; Lim, H.; Smirnov, A.; Sorokin, M.; Kenny, P.; Slutsker, I.

    2013-12-01

    Aerosols can have major implications on human health by inducing respiratory diseases due to inhalation of fine particles from biomass burning smoke or industrial pollution and on radiative forcing whereby the presence of absorbing aerosol particles (e.g., black carbon) increases atmospheric heating. Aerosol classification techniques have utilized aerosol loading and aerosol properties derived from multi-spectral and multi-angle observations by ground-based (e.g., AERONET) and satellite instrumentation (e.g., MISR). Aerosol Robotic Network (AERONET) data have been utilized to determine aerosol types by implementing various combinations of measured aerosol optical depth or retrieved size and absorption aerosol properties (e.g., Gobbi et al., 2007; Russell et al., 2010). Giles et al. [2012] showed single scattering albedo (SSA) relationship with extinction Angstrom exponent (EAE) can provide an estimate of the general classification of dominant aerosol types (i.e., desert dust, urban/industrial pollution, biomass burning smoke, and mixtures) based on data from ~20 AERONET sites located in known aerosol source regions. In addition, the absorption Angstrom exponent relationship with EAE can provide an indication of the dominant absorbing aerosol type such as dust, black carbon, brown carbon, or mixtures of them. These classification techniques are applied to the AERONET Level 2.0 quality assured data sets collected during Distributed Regional Aerosol Gridded Observational Network (DRAGON) campaigns in Maryland (USA), Japan, South Korea, Singapore, Penang (Malaysia), and California (USA). An analysis of aerosol type classification for DRAGON sites is performed as well as an assessment of the spatial variability of the aerosol types for selected DRAGON campaigns. Giles, D. M., B. N. Holben, T. F. Eck, A. Sinyuk, A. Smirnov, I. Slutsker, R. R. Dickerson, A. M. Thompson, and J. S. Schafer (2012), An analysis of AERONET aerosol absorption properties and classifications

  17. Modeling the Relationships Between Aerosol Properties and the Direct and Indirect Effects of Aerosols on Climate

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.

    1994-01-01

    Aerosols may affect climate directly by scattering and absorbing visible and infrared energy, They may also affect climate indirectly by modifying the properties of clouds through microphysical processes, and by altering abundances of radiatively important gases through heterogeneous chemistry. Researchers understand which aerosol properties control the direct effect of aerosols on the radiation budget. Unfortunately, despite an abundance of data on certain types of aerosols, much work remains to be done to determine the values of these properties. For instance we have little idea about the global distribution, seasonal variation, or interannual variability of the aerosol optical depth. Also we do not know the visible light absorption properties of tropical aerosols which may contain much debris from slash and burn agriculture. A positive correlation between aerosol concentrations and albedos of marine stratus clouds is observed, and the causative microphysics is understood. However, models suggest that it is difficult to produce new particles in the marine boundary layer. Some modelers have suggested that the particles in the marine boundary layer may originate in the free troposphere and be transported into the boundary layer. Others argue that the aerosols are created in the marine boundary layer. There are no data linking aerosol concentration and cirrus cloud albedo, and models suggest cirrus properties may not be very sensitive to aerosol abundance. There is clear evidence of a radiatively significant change in the global lower stratospheric ozone abundance during the past few decades. These changes are caused by heterogeneous chemical reactions occurring on the surfaces of particles. The rates of these reactions depend upon the chemical composition of the particles. Although rapid advances in understanding heterogeneous chemistry have been made, much remains to be done.

  18. Critical reflectance derived from MODIS: Application for the retrieval of aerosol absorption over desert regions

    NASA Astrophysics Data System (ADS)

    Wells, Kelley C.; Martins, J. Vanderlei; Remer, Lorraine A.; Kreidenweis, Sonia M.; Stephens, Graeme L.

    2012-02-01

    The determination of aerosol direct radiative forcing over desert regions requires accurate information about the aerosol single-scattering albedo (SSA); however, the brightness of desert surfaces in the visible and near-IR range complicates the retrieval of aerosol optical properties using passive space-based measurements. Here we use the critical reflectance method to retrieve spectral aerosol absorption from space over North Africa, a desert region that is predominantly impacted by absorbing dust and biomass burning aerosol. We examine the sensitivity of the critical reflectance parameter to aerosol physical and optical properties that are representative of the region, and we find that the critical reflectance has low sensitivity to assumptions of aerosol size and refractive index for dust-like particles, except at scattering angles near 180°, which should be avoided with this method. We use our findings to retrieve spectral SSA from critical reflectance derived from Moderate Resolution Imaging Spectroradiometer (MODIS) reflectances in the vicinity of two Aerosol Robotic Network (AERONET) stations: Tamanrasset, in the Algerian Sahara, and Banizoumbou, in the Sahel. We retrieve lower aerosol SSAs at Banizoumbou, which is often impacted by dust-smoke mixtures, and higher SSAs at Tamanrasset, where pure desert dust is the dominant aerosol. Our results generally fall within the AERONET uncertainty envelopes, although at Banizoumbou we retrieve a spectral dependence different from that of AERONET. On the basis of our analysis, we expect to be able to retrieve SSA from critical reflectance for pure dust with an uncertainty of 0.02 and to provide spatial and spectral SSA information that will help reduce current uncertainties in the aerosol radiative forcing over desert regions.

  19. Chemical Properties of Combustion Aerosols: An Overview

    EPA Science Inventory

    A wide variety of pyrogenic and anthropogenic sources emit fine aerosols to the atmosphere. The physical and chemical properties of these aerosols are of interest due to their influence on climate, human health, and visibility. Aerosol chemical composition is remarkably complex. ...

  20. Biomass Burning Aerosol Absorption Measurements with MODIS Using the Critical Reflectance Method

    NASA Technical Reports Server (NTRS)

    Zhu, Li; Martins, Vanderlei J.; Remer, Lorraine A.

    2010-01-01

    This research uses the critical reflectance technique, a space-based remote sensing method, to measure the spatial distribution of aerosol absorption properties over land. Choosing two regions dominated by biomass burning aerosols, a series of sensitivity studies were undertaken to analyze the potential limitations of this method for the type of aerosol to be encountered in the selected study areas, and to show that the retrieved results are relatively insensitive to uncertainties in the assumptions used in the retrieval of smoke aerosol. The critical reflectance technique is then applied to Moderate Resolution Imaging Spectrometer (MODIS) data to retrieve the spectral aerosol single scattering albedo (SSA) in South African and South American 35 biomass burning events. The retrieved results were validated with collocated Aerosol Robotic Network (AERONET) retrievals. One standard deviation of mean MODIS retrievals match AERONET products to within 0.03, the magnitude of the AERONET uncertainty. The overlap of the two retrievals increases to 88%, allowing for measurement variance in the MODIS retrievals as well. The ensemble average of MODIS-derived SSA for the Amazon forest station is 0.92 at 670 nm, and 0.84-0.89 for the southern African savanna stations. The critical reflectance technique allows evaluation of the spatial variability of SSA, and shows that SSA in South America exhibits higher spatial variation than in South Africa. The accuracy of the retrieved aerosol SSA from MODIS data indicates that this product can help to better understand 44 how aerosols affect the regional and global climate.

  1. Measurements of the absorption coefficient of stratospheric aerosols

    NASA Technical Reports Server (NTRS)

    Ogren, J. A.; Ahlquist, N. C.; Clarke, A. D.; Charlson, R. J.

    1981-01-01

    The absorption coefficients of stratospheric aerosols are measured using a variation on the integrating plate method. The technique is based on the decrease in the transparency of a substrate when an absorbing aerosol is deposited on it. A Lambert scatterer is placed behind the substrate to integrate forward scattered light and minimize the effect of scattering on the measurement. The low pressure in the stratosphere is used for the direct impaction of particles onto a narrow strip of opal glass. The eight samples collected had a median value of 4 x 10 to the -9th m with an uncertainty of + or - 5 x 10 to the -9th m. If this absorption is due to graphitic carbon, then its concentration is estimated at about 0.4 ng/cu m, or about 0.25% of the total aerosol mass concentration. Estimates of the aerosol scattering coefficients based on satellite extinction inversions result in an aerosol single-scattering albedo in the range of 0.96-1.0.

  2. Attribution of aerosol light absorption to black carbon and volatile aerosols.

    PubMed

    Shrestha, Rijana; Kim, Sang-Woo; Yoon, Soon-Chang; Kim, Ji-Hyoung

    2014-08-01

    We investigated the contribution of volatile aerosols in light-absorption measurement by three filter-based optical instruments [aethalometer, continuous light-absorption photometer (CLAP), and continuous soot monitoring system (COSMOS)] at Gosan Climate Observatory (GCO) from February to June 2012. The aerosol absorption coefficient (σ abs) and the equivalent black carbon (BC) mass concentration (M BC) measured by the aethalometer and CLAP showed good agreement with a difference of 9 %, which is likely due to the instrumental uncertainty. However, σ abs and M BC measured by the COSMOS with a heated inlet were found to be approximately 44 and 49 % lower than those measured by the aethalometer and CLAP under ambient conditions, respectively. This difference can be attributed to the light absorption by the volatile aerosols coexisting with the BC. Even considering inherent observational uncertainty, it suggests that approximately 35-40 % difference in the σ abs and M BC can be contributed by volatile aerosols. Increase in the difference of M BC measured by the aethalometer and COSMOS with the increasing thermal organic carbon (OC) measured by Sunset OC/EC analyzer further suggests that the filter-based optical instruments without the use of a heater are likely to enhance the value of σ abs and M BC, because this sample air may contain both BC and volatile aerosols.

  3. Critical Reflectance Derived from MODIS: Application for the Retrieval of Aerosol Absorption over Desert Regions

    NASA Technical Reports Server (NTRS)

    Wells, Kelley C.; Martins, J. Vanderlei; Remer, Lorraine A.; Kreidenweis, Sonia M.; Stephens, Graeme L.

    2012-01-01

    Aerosols are tiny suspended particles in the atmosphere that scatter and absorb sunlight. Smoke particles are aerosols, as are sea salt, particulate pollution and airborne dust. When you look down at the earth from space sometimes you can see vast palls of whitish smoke or brownish dust being transported by winds. The reason that you can see these aerosols is because they are reflecting incoming sunlight back to the view in space. The reason for the difference in color between the different types of aerosol is that the particles arc also absorbing sunlight at different wavelengths. Dust appears brownish or reddish because it absorbs light in the blue wavelengths and scatters more reddish light to space, Knowing how much light is scattered versus how much is absorbed, and knowin that as a function of wavelength is essential to being able to quantify the role aerosols play in the energy balance of the earth and in climate change. It is not easy measuring the absorption properties of aerosols when they are suspended in the atmosphere. People have been doing this one substance at a time in the laboratory, but substances mix when they are in the atmosphere and the net absorption effect of all the particles in a column of air is a goal of remote sensing that has not yet been completely successful. In this paper we use a technique based on observing the point at which aerosols change from brightening the surface beneath to darkening it. If aerosols brighten a surface. they must scatter more light to space. If they darken the surface. they must be absorbing more. That cross over point is called the critical reflectance and in this paper we show that critical reflectance is a monotonic function of the intrinsic absorption properties of the particles. This parameter we call the single scattering albedo. We apply the technique to MODIS imagery over the Sahara and Sahel regions to retrieve the single scattering albedo in seven wavelengths, compare these retrievals to ground

  4. Aerosol Absorption Near Beijing During EAST-AIRE

    NASA Astrophysics Data System (ADS)

    Yang, M.; Howell, S.; Huebert, B.; Zhuang, J.

    2006-12-01

    To understand the aerosol absorption that had been observed offshore during ACE-Asia, we took a suite of instruments (including a 7 wavelength aethalometer) to a site 70 km ESE of Beijing in March of 2005 to measure the wavelength dependence of aerosol absorption as a part of the EAST-AIRE program. Confidence in filter methods suffers a bit because several corrections are required to estimate ambient absorption from particles on a filter: there is enhancement by multiple scatter from the filter's matrix, shadowing by thick cakes of collected particles, and scattering by co-collected aerosols, to name a few. We encountered mild dust, heavy pollution, relatively clean air, coal-burning chimney plumes, industrial plumes, and biomass burning, often at separate times. The absorption Angstrom exponent was always greater than 1, averaging 1.5: in the UV and violet there is an enhanced absorption over what one would expect of black carbon. If we assume that BC is responsible for all the absorption at 950 nm and that it has an Angstrom coefficient of 1.0 (yielding a specific absorbance of about 9 m2g-1 at 550 nm), the remaining absorption Angstrom exponent in the visible averaged 3.2. However, the 370-950 nm absorption spectrum of the remainder looked very much like the clay and hematite absorption spectra published by Sokolik and Toon, including a striking UV absorption and a characteristic dip around 660 nm (e.g., not a power law shape). This is not surprising, since clay is both a frequent component of dust and is used as a binder in the charcoal briquettes that are widely used in China for heating and cooking. We found single-scatter albedos virtually always less than 0.9, averaging 0.82. In the presence of dust, the SSA increased toward the IR. We also find that the clay spectrum explains virtually all the non-BC absorption, so there must not be much brown carbon present. Our confidence in these on-filter absorption measurements is increased by the fact that we

  5. AeroCom INSITU Project: Comparing modeled and measured aerosol optical properties

    NASA Astrophysics Data System (ADS)

    Andrews, Elisabeth; Schmeisser, Lauren; Schulz, Michael; Fiebig, Markus; Ogren, John; Bian, Huisheng; Chin, Mian; Easter, Richard; Ghan, Steve; Kokkola, Harri; Laakso, Anton; Myhre, Gunnar; Randles, Cynthia; da Silva, Arlindo; Stier, Phillip; Skeie, Ragnehild; Takemura, Toshihiko; van Noije, Twan; Zhang, Kai

    2016-04-01

    AeroCom, an open international collaboration of scientists seeking to improve global aerosol models, recently initiated a project comparing model output to in-situ, surface-based measurements of aerosol optical properties. The model/measurement comparison project, called INSITU, aims to evaluate the performance of a suite of AeroCom aerosol models with site-specific observational data in order to inform iterative improvements to model aerosol modules. Surface in-situ data has the unique property of being traceable to physical standards, which is an asset in accomplishing the overall goal of bettering the accuracy of aerosols processes and the predicative capability of global climate models. Here we compare dry, in-situ aerosol scattering and absorption data from ~75 surface, in-situ sites from various global aerosol networks (including NOAA, EUSAAR/ACTRIS and GAW) with a simulated optical properties from a suite of models participating in the AeroCom project. We report how well models reproduce aerosol climatologies for a variety of time scales, aerosol characteristics and behaviors (e.g., aerosol persistence and the systematic relationships between aerosol optical properties), and aerosol trends. Though INSITU is a multi-year endeavor, preliminary phases of the analysis suggest substantial model biases in absorption and scattering coefficients compared to surface measurements, though the sign and magnitude of the bias varies with location. Spatial patterns in the biases highlight model weaknesses, e.g., the inability of models to properly simulate aerosol characteristics at sites with complex topography. Additionally, differences in modeled and measured systematic variability of aerosol optical properties suggest that some models are not accurately capturing specific aerosol behaviors, for example, the tendency of in-situ single scattering albedo to decrease with decreasing aerosol extinction coefficient. The endgoal of the INSITU project is to identify specific

  6. Synergic use of TOMS and AERONET observations for characterization of aerosol absorption

    NASA Astrophysics Data System (ADS)

    Torres, O.; Sinyuk, A.; Bhartia, P. K.; Dubovik, O.; Holben, B.

    2003-04-01

    The role of aerosol absorption on the radiative transfer balance of the earth-atmosphere system is one of the largest sources of uncertainty in the analysis of global climate change. Global measurements of aerosol single scattering albedo are, therefore, necessary to properly assess the radiative forcing effect of aerosols. Remote sensing of aerosol absorption is currently carried out using both ground (Aerosol Robotic Network) and space (Total Ozone Mapping Spectrometer) based observations. The satellite technique uses measurements of backscattered near ultraviolet radiation. Carbonaceous aerosols, resulting from the combustion of biomass, are one of the most predominant absorbing aerosol types in the atmosphere. In this presentation, TOMS and AERONET retrievals of single scattering albedo of carbonaceous aerosols, are compared for different environmental conditions: agriculture related biomass burning in South America and Africa and peat fires in Eastern Europe. The AERONET and TOMS derived aerosol absorption information are in good quantitative agreement. The most absorbing smoke is detected over the African Savanna. Aerosol absorption over the Brazilian rain forest is less absorbing. Absorption by aerosol particles resulting from peat fires in Eastern Europe is weaker than the absorption measured in Africa and South America. This analysis shows that the near UV satellite method of aerosol absorption characterization has the sensitivity to distinguish different levels of aerosol absorption. The analysis of the combined AERONET-TOMS observations shows a high degree of synergy between satellite and ground based observations.

  7. Synergic use of TOMS and Aeronet Observations for Characterization of Aerosol Absorption

    NASA Technical Reports Server (NTRS)

    Torres, O.; Bhartia, P. K.; Dubovik, O.; Holben, B.; Siniuk, A.

    2003-01-01

    The role of aerosol absorption on the radiative transfer balance of the earth-atmosphere system is one of the largest sources of uncertainty in the analysis of global climate change. Global measurements of aerosol single scattering albedo are, therefore, necessary to properly assess the radiative forcing effect of aerosols. Remote sensing of aerosol absorption is currently carried out using both ground (Aerosol Robotic Network) and space (Total Ozone Mapping Spectrometer) based observations. The satellite technique uses measurements of backscattered near ultraviolet radiation. Carbonaceous aerosols, resulting from the combustion of biomass, are one of the most predominant absorbing aerosol types in the atmosphere. In this presentation, TOMS and AERONET retrievals of single scattering albedo of carbonaceous aerosols, are compared for different environmental conditions: agriculture related biomass burning in South America and Africa and peat fires in Eastern Europe. The AERONET and TOMS derived aerosol absorption information are in good quantitative agreement. The most absorbing smoke is detected over the African Savanna. Aerosol absorption over the Brazilian rain forest is less absorbing. Absorption by aerosol particles resulting from peat fires in Eastern Europe is weaker than the absorption measured in Africa and South America. This analysis shows that the near UV satellite method of aerosol absorption characterization has the sensitivity to distinguish different levels of aerosol absorption. The analysis of the combined AERONET-TOMS observations shows a high degree of synergy between satellite and ground based observations.

  8. Optical Properties of Black and Brown Carbon Aerosols from Laboratory Combustion of Wildland Fuels

    NASA Astrophysics Data System (ADS)

    Beres, N. D.; Molzan, J.

    2015-12-01

    Aerosol light absorption in the solar spectral region (300 nm - 2300 nm) of the atmosphere is key for the direct aerosol radiative forcing, which is determined by aerosol single scattering albedo (SSA), asymmetry parameter, and by the albedo of the underlying surface. SSA is of key importance for the sign and quantity of aerosol direct radiative forcing; that is, does the aerosol make the earth look darker (heating) or whiter (cooling)? In addition, these optical properties are needed for satellite retrievals of aerosol optical depth and properties. During wildland fires, aerosol optical absorption is largely determined by black carbon (BC) and brown carbon (BrC) emissions. BC is strongly absorbing throughout the solar spectrum, while BrC absorption strongly increases toward shorter wavelength and can be neglected in the red and infrared. Optical properties of BrC emitted from wildland fires are poorly understood and need to be studied as function of fuel type and moisture content and combustion conditions. While much more is known about BC optical properties, knowledge for the ultraviolet (UV) spectral region is still lacking and critically needed for satellite remote sensing (e.g., TOMS, OMI) and for modeling of tropospheric photochemistry. Here, a project to better characterize biomass burning aerosol optical properties is described. It utilizes a laboratory biomass combustion chamber to generate aerosols through combustion of different wildland fuels of global and regional importance. Combustion aerosol optics is characterized with an integrating nephelometer to measure aerosol light scattering and a photoacoustic instrument to measure aerosol light absorption. These measurements will yield optical properties that are needed to improve qualitative and quantitative understanding of aerosol radiative forcing and satellite retrievals for absorbing carbonaceous aerosols from combustion of wildland fuels.

  9. Aerosol properties in Titan's upper atmosphere

    NASA Astrophysics Data System (ADS)

    Lavvas, Panayotis; Koskinen, Tommi; Royer, Emilie; Rannou, Pascal; West, Robert

    2016-06-01

    Multiple Cassini observations reveal that the abundant aerosol particles in Titan's atmosphere are formed at high altitudes, particularly in the thermosphere. They subsequently fall towards the lower atmosphere and in their path their size, shape, and population change in reflection to the variable atmospheric condition. Although multiple observations can help us retrieve information for the aerosol properties in the lower atmosphere, we have limited information for the aerosol properties between their formation region in the thermosphere and the upper region of the main haze layer or the detached aerosol layer. Observations at UV wavelengths are the only way to probe this part of the atmosphere and help us retrieve the aerosol properties. The presentation will provide an overview of the available observations, and discuss their implications for the production and evolution of Titan's aerosols.

  10. Cloud-Driven Changes in Aerosol Optical Properties - Final Technical Report

    SciTech Connect

    Ogren, John A.; Sheridan, Patrick S.; Andrews, Elisabeth

    2007-09-30

    The optical properties of aerosol particles are the controlling factors in determining direct aerosol radiative forcing. These optical properties depend on the chemical composition and size distribution of the aerosol particles, which can change due to various processes during the particles’ lifetime in the atmosphere. Over the course of this project we have studied how cloud processing of atmospheric aerosol changes the aerosol optical properties. A counterflow virtual impactor was used to separate cloud drops from interstitial aerosol and parallel aerosol systems were used to measure the optical properties of the interstitial and cloud-scavenged aerosol. Specifically, aerosol light scattering, back-scattering and absorption were measured and used to derive radiatively significant parameters such as aerosol single scattering albedo and backscatter fraction for cloud-scavenged and interstitial aerosol. This data allows us to demonstrate that the radiative properties of cloud-processed aerosol can be quite different than pre-cloud aerosol. These differences can be used to improve the parameterization of aerosol forcing in climate models.

  11. Cloud Scavenging Effects on Aerosol Radiative and Cloud-nucleating Properties - Final Technical Report

    SciTech Connect

    Ogren, John A.; Sheridan, Patrick S.; Andrews, Elisabeth

    2009-03-05

    The optical properties of aerosol particles are the controlling factors in determining direct aerosol radiative forcing. These optical properties depend on the chemical composition and size distribution of the aerosol particles, which can change due to various processes during the particles’ lifetime in the atmosphere. Over the course of this project we have studied how cloud processing of atmospheric aerosol changes the aerosol optical properties. A counterflow virtual impactor was used to separate cloud drops from interstitial aerosol and parallel aerosol systems were used to measure the optical properties of the interstitial and cloud-scavenged aerosol. Specifically, aerosol light scattering, back-scattering and absorption were measured and used to derive radiatively significant parameters such as aerosol single scattering albedo and backscatter fraction for cloud-scavenged and interstitial aerosol. This data allows us to demonstrate that the radiative properties of cloud-processed aerosol can be quite different than pre-cloud aerosol. These differences can be used to improve the parameterization of aerosol forcing in climate models.

  12. Is There a Common Correction for Biases in Historic Filter-Based Aerosol Absorption Measurements?

    NASA Astrophysics Data System (ADS)

    McComiskey, A. C.; Jefferson, A.; Dubey, M. K.; Aiken, A. C.; Fast, J. D.; Flynn, C. J.; Kassianov, E.

    2014-12-01

    Improved characterization of aerosol absorption is a pressing need for improving estimates of climate forcing by aerosols. Measurements of aerosol absorption are difficult to make with the accuracy and precision demanded by climate science. While several different approaches have been employed and new techniques have emerged, none can yet be considered a true 'gold standard'. Instruments that use filter-based methods have been the most widely used and are the basis of historic records. However, several studies using direct photoacoustic techniques have shown that filter-based measurements can be biased relative to these direct measurements. It has been demonstrated that this bias depends strongly on aerosol chemical composition, specifically concentration of organic mass. The wealth of information in the extensive set of historical filter-based data demands that this bias be diagnosed and corrected. A correction is critical for proper evaluation and development of chemical transport models, improved retrievals from remote sensing measurements, and integrating aerosol absorption surface and sub-orbital in situ measurements with knowledge gained from these other approaches. We have performed an intercomparison of absorption coefficients from a photoacoustic and two filter-based instruments with co-located organic mass concentrations from continuous, half-hourly averaged measurements over six months at a remote, continental site in the US (ARM SGP). The results show a bias in the filter-based measurements with organic concentration that is consistent with previous studies. Previous results come from controlled lab studies or field campaigns where absorption coefficients and organic concentrations are high and may represent aerosol close to the source. The current study is important in that these quantities are much lower and the aerosol likely more aged, representing a larger portion of the global conditions, yet shows a similar bias. This site provides other measures

  13. A study of remotely sensed aerosol properties from ground-based sun and sky scanning radiometers

    NASA Astrophysics Data System (ADS)

    Giles, David M.

    Aerosol particles impact human health by degrading air quality and affect climate by heating or cooling the atmosphere. The Indo-Gangetic Plain (IGP) of Northern India, one of the most populous regions in the world, produces and is impacted by a variety of aerosols including pollution, smoke, dust, and mixtures of them. The NASA Aerosol Robotic Network (AERONET) mesoscale distribution of Sun and sky-pointing instruments in India was established to measure aerosol characteristics at sites across the IGP and around Kanpur, India, a large urban and industrial center in the IGP, during the 2008 pre-monsoon (April-June). This study focused on detecting spatial and temporal variability of aerosols, validating satellite retrievals, and classifying the dominant aerosol mixing states and origins. The Kanpur region typically experiences high aerosol loading due to pollution and smoke during the winter and high aerosol loading due to the addition of dust to the pollution and smoke mixture during the pre-monsoon. Aerosol emissions in Kanpur likely contribute up to 20% of the aerosol loading during the pre-monsoon over the IGP. Aerosol absorption also increases significantly downwind of Kanpur indicating the possibility of the black carbon emissions from aerosol sources such as coal-fired power plants and brick kilns. Aerosol retrievals from satellite show a high bias when compared to the mesoscale distributed instruments around Kanpur during the pre-monsoon with few high quality retrievals due to imperfect aerosol type and land surface characteristic assumptions. Aerosol type classification using the aerosol absorption, size, and shape properties can identify dominant aerosol mixing states of absorbing dust and black carbon particles. Using 19 long-term AERONET sites near various aerosol source regions (Dust, Mixed, Urban/Industrial, and Biomass Burning), aerosol absorption property statistics are expanded upon and show significant differences when compared to previous work

  14. Mixing-State Sensitivity of Aerosol Absorption in the EMAC Chemistry-Climate Model

    NASA Astrophysics Data System (ADS)

    Klingmueller, Klaus; Steil, Benedikt; Bruehl, Christoph; Tost, Holger; Lelieveld, Jos

    2014-05-01

    The modelling of aerosol radiative forcing is a major cause of uncertainty in the assessment of global and regional atmospheric energy budgets and climate change. One reason is the strong dependence of the aerosol optical properties on the mixing state of aerosol components like black carbon and sulphates. Using the atmospheric chemistry-climate model EMAC, we study the radiative transfer assuming various mixing states. The aerosol optics code we employ builds on the AEROPT submodel which assumes homogeneous internal mixing utilising the volume average refractive index mixing rule. We have extended the submodel to additionally account for external mixing, partial external mixing and multilayered particles. Furthermore, we have implemented the volume average dielectric constant and Maxwell Garnett Mixing rule. We present results from regional case studies employing a new column version of the aerosol optical properties and radiative transfer code of EMAC, considering columns over China, India and Africa. The regional results are complemented by global results from a simulation for the year 2005. Our findings corroborate much stronger absorption by internal than external mixtures. Well mixed aerosol often is a good approximation for particles with a black carbon core, whereas particles with black carbon at the surface absorb significantly less. Therefore, we conclude that it is generally recommended to take the inner structure of internally mixed particles into account.

  15. Multi-wavelength measurements of aerosol optical absorption coefficients using a photoacoustic spectrometer

    NASA Astrophysics Data System (ADS)

    Liu, Qiang; Huang, Hong-Hua; Wang, Yao; Wang, Gui-Shi; Cao, Zhen-Song; Liu, Kun; Chen, Wei-Dong; Gao, Xiao-Ming

    2014-06-01

    The atmospheric aerosol absorption capacity is a critical parameter determining its direct and indirect effects on climate. Accurate measurement is highly desired for the study of the radiative budget of the Earth. A multi-wavelength (405 nm, 532 nm, 780 nm) aerosol absorption meter based on photoacoustic spectroscopy (PAS) invovling a single cylindrical acoustic resonator is developed for measuring the aerosol optical absorption coefficients (OACs). A sensitivity of 1.3 Mm-1 (at 532 nm) is demonstrated. The aerosol absorption meter is successfully tested through measuring the OACs of atmospheric nigrosin and ambient aerosols in the suburbs of Hefei city. The absorption cross section and absorption Ångström exponent (AAE) for ambient aerosol are determined for characterizing the component of the ambient aerosol.

  16. Light absorption of black and brown carbon aerosols: comparison of an inventory-based model estimate and observations

    NASA Astrophysics Data System (ADS)

    Feng, Y.; Liu, X.

    2015-12-01

    Spectrally resolved absorption measurements have been used to attribute the absorption and radiative effects due to brown carbon (BrC), and suggest a significant contribution. Since black carbon (BC) and BrC are co-emitted from combustion and burning processes, BrC absorption in global models has either been implicitly included in absorption by BC or more recently, characterized by a global constant refractive index. An inventory-based optical treatment for the brown carbon absorption has been developed for primary organic aerosol emissions. Results of a simple radiative transfer model with a global emission inventory show that the BrC absorptivity leads to a ˜27% reduction in the cooling effect by organic aerosols compared to the non-absorbing assumption. Here we implement the wavelength-dependent absorption properties of brown carbon parameterized as a function of BC to organic carbon ratio into a global climate model (CAM5) for different fuel emission sectors and biomass burning. This version of CAM5 also simulates the aging of freshly emitted BC and BrC into the aged accumulation-mode aerosols due to condensation of sulfate and organics. The calculated aerosol light absorption properties and spectral dependence will be compared with ground-based AERONET measurements and field observations available. Sensitivity studies of BrC radiative effects based on a global constant refractive index and the inventory-based method in this study will be discussed.

  17. Climatology and Characteristics of Aerosol Optical Properties in the Arctic

    NASA Astrophysics Data System (ADS)

    Schmeisser, Lauren; Ogren, John; Backman, John; Asmi, Eija; Andrews, Elisabeth; Jefferson, Anne; Bergin, Michael; Tunved, Peter; Sharma, Sangeeta; Starkweather, Sandra

    2016-04-01

    Within the Arctic, climate forcers like atmospheric aerosols are important contributors to the observed warming and environmental changes in the region. Quantifying the forcing by aerosols in the Arctic is especially difficult, given short aerosol lifetimes, annual variability in illumination and surface albedo, stratified atmospheric conditions, complex feedbacks, and long-range aerosol transport. However, in-situ surface measurements of Arctic aerosol optical properties can be used to constrain variability of light scattering and absorption, identify potential particle sources, and help evaluate the resulting forcing. Data from six WMO Global Atmosphere Watch stations are presented: Alert, Canada (ALT); Barrow, Alaska (BRW); Pallas, Finland (PAL); Summit, Greenland (SUM); Tiksi, Russia (TIK); and Zeppelin Mountain, Norway (ZEP). These sites contribute to the International Arctic System for Observing the Atmosphere (IASOA), which facilitates Arctic-wide data collection and analysis. Climatologies of aerosol optical properties from each station show differences in magnitude and variability of observed parameters. For example, most stations (ALT, BRW, SUM, TIK, ZEP) experience maximum scattering in winter/spring, while PAL exhibits maximum scattering in the summer. The observed range in scattering across these sites is large (almost an order of magnitude) - SUM has the lowest annual median scattering at 0.82 Mm-1 while BRW has the highest at 6.9 Mm-1. A closer look at systematic variability between optical properties at each station, as well as site back trajectories, suggest differences in aerosol processes, sources and transport. The development of consistent climatologies and additional analyses like the ones presented here can help provide a better understanding of trans-Arctic aerosol variability, which can be an asset for improving aerosol models in this unique and remote region.

  18. Black carbon and wavelength-dependent aerosol absorption in the North China Plain based on two-year aethalometer measurements

    NASA Astrophysics Data System (ADS)

    Ran, L.; Deng, Z. Z.; Wang, P. C.; Xia, X. A.

    2016-10-01

    Light-absorbing components of atmospheric aerosols have gained particular attention in recent years due to their climatic and environmental effects. Based on two-year measurements of aerosol absorption at seven wavelengths, aerosol absorption properties and black carbon (BC) were investigated in the North China Plain (NCP), one of the most densely populated and polluted regions in the world. Aerosol absorption was stronger in fall and the heating season (from November to March) than in spring and summer at all seven wavelengths. Similar spectral dependence of aerosol absorption was observed in non-heating seasons despite substantially strong absorption in fall. With an average absorption Angström exponent (α) of 1.36 in non-heating seasons, freshly emitted BC from local fossil fuel burning was thought to be the major component of light-absorbing aerosols. In the heating season, strong ultraviolet absorption led to an average α of 1.81, clearly indicating the importance of non-BC light-absorbing components, which were possibly from coal burning for domestic heating and aging processes on a regional scale. Diurnally, the variation of BC mass concentrations experienced a double-peak pattern with a higher level at night throughout the year. However, the diurnal cycle of α in the heating season was distinctly different from that in non-heating seasons. α peaked in the late afternoon in non-heating seasons with concomitantly observed low valley in BC mass concentrations. In contrast, α peaked around the midnight in the heating season and lowered down during the daytime. The relationship of aerosol absorption and winds in non-heating seasons also differed from that in the heating season. BC mass concentrations declined while α increased with increasing wind speed in non-heating seasons, which suggested elevated non-BC light absorbers in transported aged aerosols. No apparent dependence of α on wind speed was found in the heating season, probably due to well mixed

  19. Mixing state and spectral absorption of atmospheric aerosols observed at a marine background site

    NASA Astrophysics Data System (ADS)

    Cayetano, M. G.; Lee, K. Y.; Kim, Y. J.

    2011-12-01

    Mineral dust and sea salt particles are portions of atmospheric aerosols in Korea due to the periodic transport of loess dust particles from Gobi and Taklimakan deserts in west China, as well as the sea salt enrichment of atmospheric particles from the seas surrounding the Korean peninsula [Kim et al., 2009; Sahu et al., 2009]. Carbonaceous particles and secondary inorganic aerosols (sulphates and nitrates) are ubiquitous due to the proliferating biomass burning [Ryu et al., 2004], as well as the increasing use of fossil fuels locally and by regional transport from neighbouring countries. Collectively, when these aerosols are transported, their compositions are further modified due to the aging process, impacting their physico-chemical properties including spectral absorption. In order to investigate the spectral response of the absorption under different ambient aerosol conditions, measurements have been conducted at a marine background site in Korea (Deokjeok Island. 37° 13' 33" N, 126° 8' 51" E) during the spring (13 days) and fall (8 days) seasons of 2009 using an aethalometer (Magee AE31), a nephelometer (Optec NGN2a) and other supporting instruments (PILS-IC, PM2.5 cyclone samplers for off-line OC/EC measurements). It has been found that spring aerosols were dominated by sulphate-rich and carbonaceous-rich fractions (21.4%±8.0% and 28.8%±7.9%, respectively), with an Angström exponent of absorption, αabs = 1.3±0.1 at 370-950 nm. The fall season aerosols were grouped based on their chemical composition as acidic aerosols, dust-enriched, and seasalt-enriched aerosols. Angström exponent of absorption, αabs for acidic aerosols was obtained to be 1.3±0.2 at 370-950 nm. However, dust enriched aerosols showed increased absorption in the short UV-Vis range (370-590 nm), which can be attributed to their mixing with light absorbing aerosols. Different types of aerosols exhibit different spectral absorption characteristics depending on their composition and

  20. Evolution of wavelength-dependent mass absorption cross sections of carbonaceous aerosols during the 2010 DOE CARES campaign

    NASA Astrophysics Data System (ADS)

    Flowers, B. A.; Dubey, M. K.; Subramanian, R.; Sedlacek, A. J.; Kelley, P.; Luke, W. T.; Jobson, B. T.; Zaveri, R. A.

    2011-12-01

    Predictions of aerosol radiative forcing require process level optical property models that are built on precise and accurate field observations. Evolution of aerosol optical properties for urban influenced carbonaceous aerosol undergoing transport and mixing with rural air masses was a focal point of the DOE Carbonaceous Aerosol and Radiative Effects (CARES) campaign near Sacramento, CA in summer 2010. Urban aerosol was transported from Sacramento, CA (T0) to the foothills of the Sierra Nevada Mountains to a rural site located near Cool, CA (T1). Aerosol absorption and scattering coefficients were measured at the T0 and T1 sites using integrated photoacoustic acoustic/nephelometer instruments (PASS-3 and PASS-UV) at 781, 532, 405, and 375 nm. Single particle soot photometry (SP2) instrumentation was used to monitor black carbon (BC) mass at both sites. Combining data from these sensors allows estimate of the wavelength-dependent mass absorption coefficient (MAC(λ)) and partitioning of MAC(λ) into contributions from the BC core and from enhancements from coating of BC cores. MAC(λ) measured in this way is free of artifacts associated with filter-based aerosol absorption measurements and takes advantage of the single particle sensitivity of the SP2 instrument, allowing observation of MAC(λ) on 10 minute and faster time scales. Coating was observed to enhance MAC(λ) by 20 - 30 % and different wavelength dependence for MAC(λ) was observed for urban and biomass burning aerosol. Further, T0 - T1 evolution of MAC(λ) was correlated with separately measured NO/NOy ratios and CO/CO2 ratios to understand the effects of aging & transport on MAC(λ) and the implications of aerosol processing that links air quality to radiative forcing on a regional scale. Aircraft observations made from the Gulfstream-1 during CARES are also analyzed to enhance process level understanding of the optical properties of fresh and aged carbonaceous aerosol in the urban-rural interface.

  1. Aerosol absorption retrievals from the PACE broad spectrum Ocean Color Instrument (OCI)

    NASA Astrophysics Data System (ADS)

    Mattoo, S.; Remer, L. A.; Levy, R. C.; Torres, O.; Gupta, P.; Ahmad, Z.

    2015-12-01

    The PACE (Pre- Aerosol, Clouds and ocean Ecosystem) mission, anticipated for launch in the early 2020s is designed to characterize oceanic and atmospheric properties. The primary instrument on-board will be a moderate resolution (~1 km nadir) radiometer, called the Ocean Color Instrument (OCI). OCI's main purpose will be to enhance current science in aquatic biogeochemistry by offering greater capability than either MODIS or SeaWiFS. To do so, OCI will provide high spectral resolution (5 nm) from the UV to NIR (350 - 800 nm), with additional spectral bands in the NIR and SWIR to support atmospheric correction. Supplementary instruments, such as a multi-angle imaging polarimeter are also being discussed, and these supplementary instruments are associated with the atmospheric objectives of the mission, although they may also offer important new measurements for oceanic objectives. However, the OCI itself is an excellent instrument for atmospheric objectives, providing measurements across a broad spectral range that in essence combines the capabilities of MODIS and OMI, but with the UV channels from OMI to be available at moderate resolution. In preparation for the PACE mission we have begun the theoretical work necessary to create a robust, operational aerosol retrieval for OCI. This retrieval is based on the MODIS Dark Target aerosol retrieval over ocean that returns aerosol optical depth and an estimate of aerosol size distribution. It then uses these retrieved parameters to constrain a retrieval of aerosol absorption in the UV, using the OCI UV channels. The algorithm is described and its sensitivity to retrieval assumptions is tested. The goal is to understand the limitations of such an algorithm and under what conditions could we expect to obtain quantitative aerosol absorption information from OCI on PACE.

  2. Development Of A Supercontinuum Based Photoacoustic Aerosol Light Absorption And Albedo Spectrometer (PALAAS)

    NASA Astrophysics Data System (ADS)

    Arnold, Ian J.

    Aerosols are a major contributor to the global radiation budget because they modify the planetary albedo with their optical properties. These optical properties need to be measured and understood, ideally at multiple wavelengths. This thesis describes the ongoing development of a supercontinuum based multi-wavelength photoacoustic instrument to measure the light absorption and scattering coefficients of aerosols. Collimation techniques for supercontinuum sources using lens-based and off-axis parabolic mirror-based collimators were evaluated and it was determined that the off-axis mirror had superior collimation abilities for multi-spectral beams. A proof of concept supercontinuum-based photoacoustic instrument was developed using sequential measurements at multiple wavelengths. The instrument data were in good agreement with those from a commercial 3-wavelength photoacoustic instrument and the novel instrument had minimum detectable absorption and scattering coefficients of better than 4 Mm-1 and 21 Mm-1, respectively. The instrument however suffered from poor temporal resolution due to the sequential measurement and required the development of an aerosol delivery system to deliver a slowly varying aerosol concentration. In response, a spectral modulator has been developed to frequency encode different wavelength bands for simultaneous measurement with a photoacoustic instrumen.

  3. Aerosol optical properties and their radiative effects in northern China

    NASA Astrophysics Data System (ADS)

    Li, Zhanqing; Xia, Xiangao; Cribb, Maureen; Mi, Wen; Holben, Brent; Wang, Pucai; Chen, Hongbin; Tsay, Si-Chee; Eck, T. F.; Zhao, Fengsheng; Dutton, E. G.; Dickerson, R. E.

    2007-11-01

    As a fast developing country covering a large territory, China is experiencing rapid environmental changes. High concentrations of aerosols with diverse properties are emitted in the region, providing a unique opportunity for understanding the impact of environmental changes on climate. Until very recently, few observational studies were conducted in the source regions. The East Asian Study of Tropospheric Aerosols: An International Regional Experiment (EAST-AIRE) attempts to characterize the physical, optical and chemical properties of the aerosols and their effects on climate over China. This study presents some preliminary results using continuous high-quality measurements of aerosol, cloud and radiative quantities made at the first EAST-AIRE baseline station at Xianghe, about 70 km east of Beijing over a period of one year (September 2004 to September 2005). It was found that the region is often covered by a thick layer of haze (with a yearly mean aerosol optical depth equal to 0.82 at 500 nm and maximum greater than 4) due primarily to anthropogenic emissions. An abrupt "cleanup" of the haze often took place in a matter of one day or less because of the passage of cold fronts. The mean single scattering albedo is approximately 0.9 but has strong day-to-day variations with maximum monthly averages occurring during the summer. Large aerosol loading and strong absorption lead to a very large aerosol radiative effect at the surface (the annual 24-hour mean values equals 24 W m-2), but a much smaller aerosol radiative effect at the top of the atmosphere (one tenth of the surface value). The boundary atmosphere is thus heated dramatically during the daytime, which may affect atmospheric stability and cloud formation. In comparison, the cloud radiative effect at the surface is only moderately higher (-41 W m-2) than the aerosol radiative effect at the surface.

  4. Photoacoustic determination of optical absorption to extinction ratio in aerosols.

    PubMed

    Roessler, D M; Faxvog, F R

    1980-02-15

    The photoacoustic technique has been used in conjunction with an optical transmission measurement to determine the fraction of light absorbed in cigarette and acetylene smoke aerosols. At 0.5145-microm wavelength,the absorption-to-extinction fraction is 0.01 +/- 0.003 for cigarette smoke and is in excellent agreement with predictions from Mie theory for smoke particles having a refractive index of 1.45-0.00133i and a median diameter in the 0.15-0.65-microm range. For acetylene smoke the absorbed fraction was 0.85 +/- 0.05. PMID:20216896

  5. Properties of aerosol processed by ice clouds

    NASA Astrophysics Data System (ADS)

    Rudich, Y.; Adler, G.; Moise, T.; Erlick-Haspel, C.

    2012-12-01

    We suggest that highly porous aerosol (HPA) can form in the upper troposphere/lower stratosphere when ice particles encounter sub-saturation leading to ice sublimation similar to freeze drying. This process can occur at the lower layers of cirrus clouds (few km), at anvils of high convective clouds and thunderstorms, in clouds forming in atmospheric gravitational waves, in contrails and in high convective clouds injecting to the stratosphere. A new experimental system that simulates freeze drying of proxies for atmospheric aerosol at atmospheric pressure was constructed and various proxies for atmospheric soluble aerosol were studied. The properties of resulting HPA were characterized by various methods. It was found that the resulting aerosol have larger sizes (extent depends on substance and mixing), lower density (largevoid fraction), lower optical extinction and higher CCN activity and IN activity. Implication of HPA's unique properties and their atmospheric consequences to aerosol processing in ice clouds and to cloud cycles will be discussed.

  6. Global Analysis of Aerosol Properties Above Clouds

    NASA Technical Reports Server (NTRS)

    Waquet, F.; Peers, F.; Ducos, F.; Goloub, P.; Platnick, S. E.; Riedi, J.; Tanre, D.; Thieuleux, F.

    2013-01-01

    The seasonal and spatial varability of Aerosol Above Cloud (AAC) properties are derived from passive satellite data for the year 2008. A significant amount of aerosols are transported above liquid water clouds on the global scale. For particles in the fine mode (i.e., radius smaller than 0.3 m), including both clear sky and AAC retrievals increases the global mean aerosol optical thickness by 25(+/- 6%). The two main regions with man-made AAC are the tropical Southeast Atlantic, for biomass burning aerosols, and the North Pacific, mainly for pollutants. Man-made AAC are also detected over the Arctic during the spring. Mineral dust particles are detected above clouds within the so-called dust belt region (5-40 N). AAC may cause a warming effect and bias the retrieval of the cloud properties. This study will then help to better quantify the impacts of aerosols on clouds and climate.

  7. Aerosol physical properties from satellite horizon inversion

    NASA Technical Reports Server (NTRS)

    Gray, C. R.; Malchow, H. L.; Merritt, D. C.; Var, R. E.; Whitney, C. K.

    1973-01-01

    The feasibility is investigated of determining the physical properties of aerosols globally in the altitude region of 10 to 100 km from a satellite horizon scanning experiment. The investigation utilizes a horizon inversion technique previously developed and extended. Aerosol physical properties such as number density, size distribution, and the real and imaginary components of the index of refraction are demonstrated to be invertible in the aerosol size ranges (0.01-0.1 microns), (0.1-1.0 microns), (1.0-10 microns). Extensions of previously developed radiative transfer models and recursive inversion algorithms are displayed.

  8. Light absorption properties of brown carbon in the high Himalayas

    NASA Astrophysics Data System (ADS)

    Kirillova, Elena N.; Marinoni, Angela; Bonasoni, Paolo; Vuillermoz, Elisa; Facchini, Maria Cristina; Fuzzi, Sandro; Decesari, Stefano

    2016-08-01

    The light-absorbing properties of water-soluble brown carbon (WS-BrC) and methanol-soluble brown carbon (MeS-BrC) were studied in PM10 aerosols collected at the "Nepal Climate Observatory-Pyramid" (NCO-P) station (5079 m above sea level) during the period 2013-2014. The light absorption coefficients of WS-BrC and MeS-BrC were the highest during the premonsoon season and the lowest during monsoon. MeS-BrC absorbs about 2 times higher at 365 nm and about 3 times more at 550 nm compared to WS-BrC. The mass absorption cross section (MAC) of WS-BrC measured at 365 nm is similar to that observed previously at South Asian low-altitude sites. Fractional solar radiation absorption by BrC compared to BC considering the full solar spectrum showed that WS-BrC absorbs 4 ± 1% and MeS-BrC absorbs 9 ± 2% compared to BC at NCO-P. Such ratios become 8 ± 1% (for WS-BrC respect to BC) and 17 ± 5% (for MeS-BrC respect to BC) when accounting for correction factors proposed by previous studies to convert absorption coefficients in bulk solutions into light absorption by accumulation mode aerosol particles. These results confirm the importance of BrC in contributing to light-absorbing aerosols in this region of the world. However, the BrC absorption at 550 nm appears small compared to that of BC (1-5%, or 3-9% with conversion factors), and it is lower compared to global model estimates constrained by Aerosol Robotic Network observations. Finally, our study provides no clear evidence of a change in the fractional contribution of BrC with respect to BC to light absorption in the middle troposphere respect to the Indo-Gangetic plain boundary layer.

  9. Global Aerosol Radiative Forcing Derived from Sea WiFS-Inferred Aerosol Optical Properties

    NASA Technical Reports Server (NTRS)

    Chou, Ming-Dah; Chan, Pui-King; Wang, Menghua

    1999-01-01

    Aerosol optical properties inferred from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) radiance measurements are used to compute the aerosol shortwave radiative forcing using a radiative transfer model. The aerosol optical thickness at the wavelength of 865-nm is taken from the SeaWIFS archive. It is found that the nominal optical thickness over oceans ranges from 0.1 to 0.2. Using a maritime aerosol model and the radiances measured at the various SeaWiFS channels, the Angstrom exponent is determined to be 0.2174, the single-scattering albedo to be 0.995, and the asymmetry factor to be 0.786. The radiative transfer model has eight bands in the visible and ultraviolet spectral regions and three bands in the near infrared. It includes the absorption due to aerosols, water vapor, carbon dioxide, and oxygen, and the scattering due to aerosols and gases (Rayleigh scattering). The radiative forcing is computed over global oceans for four months (January, April, July, and October, 1998) to represent four seasons. It is found that the aerosol radiative forcing is large and changes significantly with seasons near the continents with large-scale forest fires and desert dust. Averaged over oceans and the four months, the aerosol radiative forcing is approximately 7 W/sq m at the top of the atmosphere. This large radiative forcing is expected to have a significant cooling effect on the Earth's climate as implied from simulations of a number of general circulation models.

  10. Columnar aerosol optical properties at AERONET sites in central eastern Asia and aerosol transport to the tropical mid-Pacific

    NASA Astrophysics Data System (ADS)

    Eck, T. F.; Holben, B. N.; Dubovik, O.; Smirnov, A.; Goloub, P.; Chen, H. B.; Chatenet, B.; Gomes, L.; Zhang, X.-Y.; Tsay, S.-C.; Ji, Q.; Giles, D.; Slutsker, I.

    2005-03-01

    The column-integrated optical properties of aerosol in the central eastern region of Asia and midtropical Pacific were investigated based on Sun/sky radiometer measurements made at Aerosol Robotic Network (AERONET) sites in these regions. Characterization of aerosol properties in the Asian region is important due to the rapid growth of both population and economic activity, with associated increases in fossil fuel combustion, and the possible regional and global climatic impacts of related aerosol emissions. Multiyear monitoring over the complete annual cycle at sites in China, Mongolia, South Korea, and Japan suggest spring and/or summer maximum in aerosol optical depth (τa) and a winter minimum; however, more monitoring is needed to establish accurate climatologies. The annual cycle of Angstrom wavelength exponent (α) showed a springtime minimum associated with dust storm activity; however, the monthly mean α440-870 was >0.8 even for the peak dust season at eastern Asian sites suggesting that fine mode pollution aerosol emitted from population centers in eastern Asia dominates the monthly aerosol optical influence even in spring as pollution aerosol mixes with coarse mode dust originating in western source regions. Aerosol optical depth peaks in spring in the tropical mid-Pacific Ocean associated with seasonal shifts in atmospheric transport from Asia, and ˜35% of the springtime τa500 enhancement occurs at altitudes above 3.4 km. For predominately fine mode aerosol pollution cases, the average midvisible (˜550 nm) single scattering albedo (ω0) at two continental urban sites in China averaged ˜0.89, while it was significantly higher, ˜0.93, at two relatively rural coastal sites in South Korea and Japan. Differences in fine mode absorption between these regions may result from a combination of factors including aerosol aging during transport, relative humidity differences, sea salt at coastal sites, and fuel type and combustion differences in the two

  11. Microphysical and Chemical Properties of Agricultural Aerosols

    NASA Astrophysics Data System (ADS)

    Brooks, S. D.; Moon, S.; Littleton, R.; Auvermann, B.

    2005-12-01

    Due to significant atmospheric loadings of agricultural dust aerosols, the aerosol's ability to contribute significantly to climate forcing on a regional to global level has been a topic of recent interest. Efforts have been made to quantify both the aerosol extinction of the total aerosol population and the hygroscopic and chemical properties of individual particles at a cattle feedyard near Canyon, Texas. Measurements of aerosol extinction are made using open-path transmissometry. Our results show that extinction varies significantly with relative humidity. To further explore the hygroscopic nature of the particles, size-resolved aerosol samples are collected using a cascade impactor system (7 stages ranging from 0.6 micron to 16 micron diameter) and hygroscopicity measurements are conducted on these using an Environmental Scanning Electron Microscope (ESEM). Complimentary determination of the elemental composition of individual particles is performed using Energy Dispersive X-ray Spectroscopy. Results of the optical properties, hygroscopicity and chemical composition of aerosols will be presented and atmospheric implications discussed.

  12. Atmospheric aerosols: Their Optical Properties and Effects (supplement)

    NASA Technical Reports Server (NTRS)

    1976-01-01

    A digest of technical papers is presented. Topics include aerosol size distribution from spectral attenuation with scattering measurements; comparison of extinction and backscattering coefficients for measured and analytic stratospheric aerosol size distributions; using hybrid methods to solve problems in radiative transfer and in multiple scattering; blue moon phenomena; absorption refractive index of aerosols in the Denver pollution cloud; a two dimensional stratospheric model of the dispersion of aerosols from the Fuego volcanic eruption; the variation of the aerosol volume to light scattering coefficient; spectrophone in situ measurements of the absorption of visible light by aerosols; a reassessment of the Krakatoa volcanic turbidity, and multiple scattering in the sky radiance.

  13. Remote sensing of aerosol properties during CARES

    NASA Astrophysics Data System (ADS)

    Kassianov, Evgueni; Barnard, James; Pekour, Mikhail; Flynn, Connor; Ferrare, Richard; Hostetler, Chris; Hair, John; Jobson, Bertram T.

    2011-11-01

    One month of MFRSR data collected at two sites in the central California (USA) region during the CARES campaign are processed and the MFRSR-derived AODs at 500 nm wavelength are compared with available AODs provided by AERONET measurements. We find that the MFRSR and AERONET AODs are small (~0.05) and comparable. A reasonable quantitative agreement between column aerosol size distributions (up to 2 μm) from the MFRSR and AERONET retrievals is illustrated as well. Analysis of the retrieved (MFRSR and AERONET) and in situ measured aerosol size distributions suggests that the contribution of the coarse mode to aerosol optical properties is substantial for several days. The results of a radiative closure experiment performed for the two sites and one-month period show a favorable agreement between the calculated and measured broadband downwelling irradiances (bias does not exceed about 3 Wm-2), and thus imply that the MFRSR-derived aerosol optical properties are reasonable.

  14. Remote Sensing of Aerosol Properties during CARES

    SciTech Connect

    Kassianov, Evgueni I.; Barnard, James C.; Pekour, Mikhail S.; Flynn, Connor J.; Ferrare, R.; Hostetler, Chris A.; Hair, John; Jobson, Bertram Thomas

    2011-10-01

    One month of MFRSR data collected at two sites in the central California (USA) region during the CARES campaign are processed and the MFRSR-derived AODs at 500 nm wavelength are compared with available AODs provided by AERONET measurements. We find that the MFRSR and AERONET AODs are small ({approx}0.05) and comparable. A reasonable quantitative agreement between column aerosol size distributions (up to 2 um) from the MFRSR and AERONET retrievals is illustrated as well. Analysis of the retrieved (MFRSR and AERONET) and in situ measured aerosol size distributions suggests that the contribution of the coarse mode to aerosol optical properties is substantial for several days. The results of a radiative closure experiment performed for the two sites and one-month period show a favorable agreement between the calculated and measured broadband downwelling irradiances (bias does not exceed about 3 Wm-2), and thus imply that the MFRSR-derived aerosol optical properties are reasonable.

  15. Aerosol Optical Properties Measured Onboard the Ronald H. Brown During ACE Asia as a Function of Aerosol Chemical Composition and Source Region

    NASA Technical Reports Server (NTRS)

    Quinn, P. K.; Coffman, D. J.; Bates, T. S.; Welton, E. J.; Covert, D. S.; Miller, T. L.; Johnson, J. E.; Maria, S.; Russell, L.; Arimoto, R.

    2004-01-01

    During the ACE Asia intensive field campaign conducted in the spring of 2001 aerosol properties were measured onboard the R/V Ronald H. Brown to study the effects of the Asian aerosol on atmospheric chemistry and climate in downwind regions. Aerosol properties measured in the marine boundary layer included chemical composition; number size distribution; and light scattering, hemispheric backscattering, and absorption coefficients. In addition, optical depth and vertical profiles of aerosol 180 deg backscatter were measured. Aerosol within the ACE Asia study region was found to be a complex mixture resulting from marine, pollution, volcanic, and dust sources. Presented here as a function of air mass source region are the mass fractions of the dominant aerosol chemical components, the fraction of the scattering measured at the surface due to each component, mass scattering efficiencies of the individual components, aerosol scattering and absorption coefficients, single scattering albedo, Angstrom exponents, optical depth, and vertical profiles of aerosol extinction. All results except aerosol optical depth and the vertical profiles of aerosol extinction are reported at a relative humidity of 55 +/- 5%. An over-determined data set was collected so that measured and calculated aerosol properties could be compared, internal consistency in the data set could be assessed, and sources of uncertainty could be identified. By taking into account non-sphericity of the dust aerosol, calculated and measured aerosol mass and scattering coefficients agreed within overall experimental uncertainties. Differences between measured and calculated aerosol absorption coefficients were not within reasonable uncertainty limits, however, and may indicate the inability of Mie theory and the assumption of internally mixed homogeneous spheres to predict absorption by the ACE Asia aerosol. Mass scattering efficiencies of non-sea salt sulfate aerosol, sea salt, submicron particulate organic

  16. Infrared absorption by volcanic stratospheric aerosols observed by ISAMS

    SciTech Connect

    Grainger, R.G.; Lambert, A.; Taylor, F.W.; Remedios, J.J.; Rodgers, C.D.; Corney, M. ); Kerridge, B.J. )

    1993-06-18

    The upper atmosphere research satellite was lofted shortly after the Mt. Pinatubo volcano erupted, and is estimated to have injected 20 million metric tons of sulphur dioxide into the stratosphere. This gas typically is converted to sulphuric acid by interactions with water droplets in the stratosphere. These droplets are typically not saturated in acid density, so the sticking fraction is very high. The improved stratospheric and mesospheric sounder makes measurements in 14 infrared channels from 4 to 17 [mu]m. The authors have used the available infrared data channels to model the distribution and density of sulfuric acid aerosols in the stratospheric band about the equator as a result of this volcanic eruption. Knowing the spectral properties of the aerosol load will aid in modeling the radiative and climatic impacts of this volcanic ejecta.

  17. Organic Carbon and Light Absorption Analysis of Los Angeles Aerosols through an Online Sampling System

    NASA Astrophysics Data System (ADS)

    Hartley, M. K.; Hawkins, L. N.

    2013-12-01

    Brown carbon is a comprehensive term for organic compounds with wavelength dependent light absorption. Common sources of brown carbon include fossil fuel combustion, biomass burning and aqueous reactions in cloud and fog water. Nitrophenols have been proposed as one source of brown carbon in the Los Angeles area. In this work, we are interested in the relative strengths of each of these sources within Los Angeles. We have implemented a continuous online system of collection and analysis within our lab. The system consists of a particle into liquid sampler (PILS), a liquid waveguide capillary cell (LWCC) and a total organic carbon analyzer (TOC). Online analysis of organic carbon content and UV-Vis absorption has allowed us to study the ratio of the two as an intrinsic property of the aerosol particles, called the 'absorption coefficient.' Using a rearrangement of Beer's Law, we have analyzed the relationship: ɛ = A / C (where ɛ is the absorption coefficient, A is the light absorption of the sample and C is the concentration of organic carbon in the sample). Using our continuous online system, we have collected absorption spectra and total organic carbon measurements over several weeks and in varying environmental conditions. Our work has shown that different weather conditions, along with fog or cloud formation, can affect the absorption coefficient of the brown carbon compounds in the air.

  18. Light absorption by secondary organic aerosol from α-pinene: Effects of oxidants, seed aerosol acidity, and relative humidity

    SciTech Connect

    Song, Chen; Gyawali, Madhu; Zaveri, Rahul A.; Shilling, John E.; Arnott, W. Patrick

    2013-10-25

    It is well known that light absorption from dust and black carbon aerosols has a warming effect on climate while light scattering from sulfate, nitrate, and sea salt aerosols has a cooling effect. However, there are large uncertainties associated with light absorption and scattering by different types of organic aerosols, especially in the near-UV and UV spectral regions. In this paper, we present the results from a systematic laboratory study focused on measuring light absorption by secondary organic aerosols (SOAs) generated from dark α-pinene + O3 and α-pinene + NOx + O3 systems in the presence of neutral and acidic sulfate seed aerosols. Light absorption was monitored using photoacoustic spectrometers at four different wavelengths: 355, 405, 532, and 870 nm. Significant light absorption at 355 and 405 nm was observed for the SOA formed from α-pinene + O3 + NO3 system only in the presence of highly acidic sulfate seed aerosols under dry conditions. In contrast, no absorption was observed when the relative humidity was elevated to greater than 27% or in the presence of neutral sulfate seed aerosols. Organic nitrates in the SOA formed in the presence of neutral sulfate seed aerosols were found to be nonabsorbing, while the light-absorbing compounds are speculated to be aldol condensation oligomers with nitroxy organosulfate groups that are formed in highly acidic sulfate aerosols. Finally and overall, these results suggest that dark α-pinene + O3 and α-pinene + NOx + O3 systems do not form light-absorbing SOA under typical atmospheric conditions.

  19. Neutron scattering and absorption properties

    SciTech Connect

    Holden, N.E.

    1993-12-01

    The Table in this report presents an evaluated set of values for the experimental quantities, which characterize the properties for scattering and absorption of neutrons. The neutron cross section is given for room temperature neutrons, 20.43{degree}C, corresponds to a thermal neutron energy of 0.0253 electron volts (eV) or a neutron velocity of 2200 meters/second. The neutron resonance integral is defined over the energy range from 0.5 eV to 0.1 {times} 10{sup 6} eV, or 0.1 MeV. A list of the major references used is given below. The literature cutoff data is October 1993. Uncertainties are given in parentheses. Parentheses with two or more numbers indicate values to the excited states(s) and to the ground state of the product nucleus.

  20. Aerosol Light Absorption and Scattering Assessments and the Impact of City Size on Air Pollution

    NASA Astrophysics Data System (ADS)

    Paredes-Miranda, Guadalupe

    The general problem of urban pollution and its relation to the city population is examined in this dissertation. A simple model suggests that pollutant concentrations should scale approximately with the square root of city population. This model and its experimental evaluation presented here serve as important guidelines for urban planning and attainment of air quality standards including the limits that air pollution places on city population. The model was evaluated using measurements of air pollution. Optical properties of aerosol pollutants such as light absorption and scattering plus chemical species mass concentrations were measured with a photoacoustic spectrometer, a reciprocal nephelometer, and an aerosol mass spectrometer in Mexico City in the context of the multinational project "Megacity Initiative: Local And Global Research Observations (MILAGRO)" in March 2006. Aerosol light absorption and scattering measurements were also obtained for Reno and Las Vegas, NV USA in December 2008-March 2009 and January-February 2003, respectively. In all three cities, the morning scattering peak occurs a few hours later than the absorption peak due to the formation of secondary photochemically produced aerosols. In particular, for Mexico City we determined the fraction of photochemically generated secondary aerosols to be about 75% of total aerosol mass concentration at its peak near midday. The simple 2-d box model suggests that commonly emitted primary air pollutant (e.g., black carbon) mass concentrations scale approximately as the square root of the urban population. This argument extends to the absorption coefficient, as it is approximately proportional to the black carbon mass concentration. Since urban secondary pollutants form through photochemical reactions involving primary precursors, in linear approximation their mass concentration also should scale with the square root of population. Therefore, the scattering coefficient, a proxy for particulate matter

  1. Contribution of Black Carbon, Brown Carbon and Lensing Effect to Total Aerosol Absorption in Indo-Gangetic Plain

    NASA Astrophysics Data System (ADS)

    Shamjad, Pm; Tripathi, Sachchida; Bergin, Mike; Vreeland, Heidi

    2016-04-01

    This study reports the optical and physical properties of atmospheric and denuded (heated at 300°C) aerosols from Indo-Gangetic Plain (IGP) during 20 December 2014 to 28 February 2015. A Single Particle Soot Photometer (SP2) and High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) were used to measure black carbon (BC) and organic carbon (OC) in real time respectively. During experiments large scale carbonaceous aerosol loading is observed in IGP. Multiple biomass burning events are observed with varying intensity and duration. Refractive index of brown carbon (BrC) is derived from filter extracts using Liquid Core Wave Capillary Cell (LWCC). Refractive index of BrC at 405 is 4 times higher in IGP when compared to studies conducted in USA. Through Mie modelling we identified the percentage contribution of black carbon, BrC and lensing effect to total aerosol absorption. On average 75% of absorption is from black carbon alone, while rest is contributed from volatile components. Within the volatile component contribution, at 405 nm BrC contributes around 20% and rest from lensing effect. But at 781 nm lensing contributed more than BrC. Overall results indicate the special characteristics on BrC aerosols in IGP and the importance of considering spectral absorption in global aerosol modelling studies.

  2. Biogenic Aerosols Over the Amazon Basin: Optical Properties and Relationship With Elemental and Ionic Composition

    NASA Astrophysics Data System (ADS)

    Artaxo, P.; Martin, S. T.; Andreae, M. O.; Godoy, J. M.; Godoy, M. L.; Rizzo, L. V.; Paixao, M.

    2008-12-01

    We investigated the optical properties of natural biogenic aerosol particles over the central Amazon Basin near Manaus during the wet season in February and March 2008. The measurements were conducted as part of the AMAZE-08 (Amazonian Aerosol Characterization Experiment) sampling campaign. Light absorption was determined with the use of an Aethalometer and an MAAP (Multi Angle Absorption Photometer). Light scattering was measured with a 3 wavelength TSI nephelometer and an Ecotech nephelometer. The elemental composition was measured trough PIXE and IC. Single scattering albedo shows relatively low values varying from 0.86 to 0.95. Very low fine mode aerosol mass was measured, and coarse mode particles are responsible for a significant fraction of scattering and absorption. Sulfur was observed in very low concentrations, and most of the aerosol mass was organic. Long range transport of soil dust from Sahara were observed and reflected in the light scattering coefficient. Wavelength dependence of absorption indicates the strong influence of coarse mode aerosol. Aerosol optical thickness shows low values, but with significant single scattering albedo values, showing strong absorption properties of these biogenic aerosols. Size distribution measurements shows consistence with the scattering coefficients measured, if the coarse mode particles are taken into account.

  3. A closure study of aerosol optical properties at a regional background mountainous site in Eastern China.

    PubMed

    Yuan, Liang; Yin, Yan; Xiao, Hui; Yu, Xingna; Hao, Jian; Chen, Kui; Liu, Chao

    2016-04-15

    There is a large uncertainty in evaluating the radiative forcing from aerosol-radiation and aerosol-cloud interactions due to the limited knowledge on aerosol properties. In-situ measurements of aerosol physical and chemical properties were carried out in 2012 at Mt. Huang (the Yellow Mountain), a continental background mountainous site in eastern China. An aerosol optical closure study was performed to verify the model outputs by using the measured aerosol optical properties, in which a spherical Mie model with assumptions of external and core-shell mixtures on the basis of a two-component optical aerosol model and high size-segregated element carbon (EC) ratio was applied. Although the spherical Mie model would underestimate the real scattering with increasing particle diameters, excellent agreement between the calculated and measured values was achieved with correlation coefficients above 0.98. Sensitivity experiments showed that the EC ratio had a negligible effect on the calculated scattering coefficient, but largely influenced the calculated absorption coefficient. The high size-segregated EC ratio averaged over the study period in the closure was enough to reconstruct the aerosol absorption coefficient in the Mie model, indicating EC size resolution was more important than time resolution in retrieving the absorption coefficient in the model. The uncertainties of calculated scattering and absorption coefficients due to the uncertainties of measurements and model assumptions yielded by a Monte Carlo simulation were ±6% and ±14% for external mixture and ±9% and ±31% for core-shell mixture, respectively. This study provided an insight into the inherent relationship between aerosol optical properties and physicochemical characteristics in eastern China, which could supplement the database of aerosol optical properties for background sites in eastern China and provide a method for regions with similar climate.

  4. Atmospheric Aerosol Properties and Climate Impacts

    NASA Technical Reports Server (NTRS)

    Chin, Mian; Kahn, Ralph A.; Remer, Lorraine A.; Yu, Hongbin; Rind, David; Feingold, Graham; Quinn, Patricia K.; Schwartz, Stephen E.; Streets, David G.; DeCola, Phillip; Halthore, Rangasayi

    2009-01-01

    This report critically reviews current knowledge about global distributions and properties of atmospheric aerosols, as they relate to aerosol impacts on climate. It assesses possible next steps aimed at substantially reducing uncertainties in aerosol radiative forcing estimates. Current measurement techniques and modeling approaches are summarized, providing context. As a part of the Synthesis and Assessment Product in the Climate Change Science Program, this assessment builds upon recent related assessments, including the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4, 2007) and other Climate Change Science Program reports. The objectives of this report are (1) to promote a consensus about the knowledge base for climate change decision support, and (2) to provide a synthesis and integration of the current knowledge of the climate-relevant impacts of anthropogenic aerosols for policy makers, policy analysts, and general public, both within and outside the U.S government and worldwide.

  5. Relating aerosol absorption due to soot, organic carbon, and dust to emission sources determined from in-situ chemical measurements

    NASA Astrophysics Data System (ADS)

    Cazorla, A.; Bahadur, R.; Suski, K. J.; Cahill, J. F.; Chand, D.; Schmid, B.; Ramanathan, V.; Prather, K. A.

    2013-09-01

    Estimating the aerosol contribution to the global or regional radiative forcing can take advantage of the relationship between the spectral aerosol optical properties and the size and chemical composition of aerosol. Long term global optical measurements from observational networks or satellites can be used in such studies. Using in-situ chemical mixing state measurements can help us to constrain the limitations of such estimates. In this study, the Absorption Ångström Exponent (AAE) and the Scattering Ångström Exponent (SAE) derived from 10 operational AERONET sites in California are combined for deducing chemical speciation based on wavelength dependence of the optical properties. In addition, in-situ optical properties and single particle chemical composition measured during three aircraft field campaigns in California between 2010 and 2011 are combined in order to validate the methodology used for the estimates of aerosol chemistry using spectral optical properties. Results from this study indicate a dominance of mixed types in the classification leading to an underestimation of the primary sources, however secondary sources are better classified. The distinction between carbonaceous aerosols from fossil fuel and biomass burning origins is not clear, since their optical properties are similar. On the other hand, knowledge of the aerosol sources in California from chemical studies help to identify other misclassification such as the dust contribution.

  6. Strong Wavelength Dependence of Aerosol Light Absorption from Peat Combustion

    NASA Astrophysics Data System (ADS)

    Gyawali, M. S.; Chakrabarty, R. K.; Yatavelli, R. L. N.; Chen, L. W. A. A.; Knue, J.; Samburova, V.; Watts, A.; Moosmüller, H.; Arnott, W. P.; Wang, X.; Zielinska, B.; Chow, J. C.; Watson, J. G.; Tsibart, A.

    2014-12-01

    Globally, organic soils and peats may store as much as 600 Gt of terrestrial carbon, representing 20 - 30% of the planet's terrestrial organic carbon mass. This is approximately the same carbon mass as that contained in Earth's atmosphere, despite peatlands occupying only 3% of its surface. Effects of fires in these ecosystems are of global concern due to their potential for enormous carbon release into the atmosphere. The implications for contributions of peat fires to the global carbon cycle and radiative forcing scenarios are significant. Combustion of peat mostly takes place in the low temperature, smoldering phase of a fire. It consumes carbon that may have accumulated over a period of hundreds to thousands of years. In comparison, combustion of aboveground biomass fuels releases carbon that has accumulated much more recently, generally over a period of years or decades. Here, we report our findings on characterization of emissions from laboratory combustion of peat soils from three locations representing the biomes in which these soils occur. Peat samples from Alaska and Florida (USA) and Siberia (Russia) were burned at two different fuel moisture levels. Burns were conducted in an 8-m3 volume combustion chamber located at the Desert Research Institute, Reno, NV, USA. We report significant brown carbon production from combustion of all three peat soils. We used a multispectral (405, 532, 781 nm) photoacoustic instrument equipped with integrating nephelometer to measure the wavelength-dependent aerosol light absorption and scattering. Absorption Ångström exponents (between 405 and 532 nm) as high as ten were observed, revealing strongly enhanced aerosol light absorption in the violet and blue wavelengths. Single scattering albedos (SSA) of 0.94 and 0.99 were observed at 405 and 532 nm, respectively, for the same sample. Variability of these optical parameters will be discussed as a function of fuel and combustion conditions. Other real-time measurements

  7. Impact of Tropospheric Aerosol Absorption on Ozone Retrieval from buv Measurements

    NASA Technical Reports Server (NTRS)

    Torres, O.; Bhartia, P. K.

    1998-01-01

    The impact of tropospheric aerosols on the retrieval of column ozone amounts using spaceborne measurements of backscattered ultraviolet radiation is examined. Using radiative transfer calculations, we show that uv-absorbing desert dust may introduce errors as large as 10% in ozone column amount, depending on the aerosol layer height and optical depth. Smaller errors are produced by carbonaceous aerosols that result from biomass burning. Though the error is produced by complex interactions between ozone absorption (both stratospheric and tropospheric), aerosol scattering, and aerosol absorption, a surprisingly simple correction procedure reduces the error to about 1%, for a variety of aerosols and for a wide range of aerosol loading. Comparison of the corrected TOMS data with operational data indicates that though the zonal mean total ozone derived from TOMS are not significantly affected by these errors, localized affects in the tropics can be large enough to seriously affect the studies of tropospheric ozone that are currently undergoing using the TOMS data.

  8. Morphology and Optical Properties of Mixed Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Fard, Mehrnoush M.; Krieger, Ulrich; Rudich, Yinon; Marcolli, Claudia; Peter, Thomas

    2015-04-01

    Experiments and modeling studies have shown that deliquesced aerosols can be present not only as one-phase system containing organics, inorganic salts and water, but often as two-phase systems consisting of a predominantly organic and a predominantly inorganic aqueous phase 1,2. Recent laboratory studies conducted with model mixtures representing tropospheric aerosols1,2,3, secondary organic aerosol (SOA) from smog chamber experiments4, and field measurements5 suggest that liquid- liquid phase separations (LLPS) is indeed a common phenomenon in mixed organic/ ammonium sulfate (AS) particles. During LLPS, particles may adopt different morphologies mainly core- shell and partially engulfed. A core- shell configuration will have consequences for heterogeneous chemistry and hygroscopicity and as a result will alter the optical properties of the particles since the aqueous inorganic-rich phase will be totally enclosed by a probably highly viscous organic coating with low diffusivity for reactants and water. The primary objective of this project is to establish a method for investigating the morphology of mixed inorganic and absorbing organic compounds of atmospheric relevance and study their radiative properties before, during, and after phase transitions mainly during LLPS. This will be the first study looking into the radiative effect of LLPS in detail. In this first experiment, the behavior of single droplets of carminic acid (CA)/ AS/ H2O mixture was monitored during relative humidity (RH) cycles using optical microscopy. The same mixture particle was levitated in an electrodynamic balance (EDB) and the change in its absorption properties was measured at varying RH. We also intend to determine the occurrence of LLPS in accumulation- sized particles and the change in their absorption using a cavity ring down aerosol spectrometer. If LLPS alters the absorptive properties of the suggested model aerosols significantly, absorption measurements of accumulation mode

  9. Impacts of Combustion Conditions and Photochemical Processing on the Light Absorption of Biomass Combustion Aerosol.

    PubMed

    Martinsson, J; Eriksson, A C; Nielsen, I Elbæk; Malmborg, V Berg; Ahlberg, E; Andersen, C; Lindgren, R; Nyström, R; Nordin, E Z; Brune, W H; Svenningsson, B; Swietlicki, E; Boman, C; Pagels, J H

    2015-12-15

    The aim was to identify relationships between combustion conditions, particle characteristics, and optical properties of fresh and photochemically processed emissions from biomass combustion. The combustion conditions included nominal and high burn rate operation and individual combustion phases from a conventional wood stove. Low temperature pyrolysis upon fuel addition resulted in "tar-ball" type particles dominated by organic aerosol with an absorption Ångström exponent (AAE) of 2.5-2.7 and estimated Brown Carbon contributions of 50-70% to absorption at the climate relevant aethalometer-wavelength (520 nm). High temperature combustion during the intermediate (flaming) phase was dominated by soot agglomerates with AAE 1.0-1.2 and 85-100% of absorption at 520 nm attributed to Black Carbon. Intense photochemical processing of high burn rate flaming combustion emissions in an oxidation flow reactor led to strong formation of Secondary Organic Aerosol, with no or weak absorption. PM1 mass emission factors (mg/kg) of fresh emissions were about an order of magnitude higher for low temperature pyrolysis compared to high temperature combustion. However, emission factors describing the absorption cross section emitted per kg of fuel consumed (m(2)/kg) were of similar magnitude at 520 nm for the diverse combustion conditions investigated in this study. These results provide a link between biomass combustion conditions, emitted particle types, and their optical properties in fresh and processed plumes which can be of value for source apportionment and balanced mitigation of biomass combustion emissions from a climate and health perspective. PMID:26561964

  10. Impacts of Combustion Conditions and Photochemical Processing on the Light Absorption of Biomass Combustion Aerosol.

    PubMed

    Martinsson, J; Eriksson, A C; Nielsen, I Elbæk; Malmborg, V Berg; Ahlberg, E; Andersen, C; Lindgren, R; Nyström, R; Nordin, E Z; Brune, W H; Svenningsson, B; Swietlicki, E; Boman, C; Pagels, J H

    2015-12-15

    The aim was to identify relationships between combustion conditions, particle characteristics, and optical properties of fresh and photochemically processed emissions from biomass combustion. The combustion conditions included nominal and high burn rate operation and individual combustion phases from a conventional wood stove. Low temperature pyrolysis upon fuel addition resulted in "tar-ball" type particles dominated by organic aerosol with an absorption Ångström exponent (AAE) of 2.5-2.7 and estimated Brown Carbon contributions of 50-70% to absorption at the climate relevant aethalometer-wavelength (520 nm). High temperature combustion during the intermediate (flaming) phase was dominated by soot agglomerates with AAE 1.0-1.2 and 85-100% of absorption at 520 nm attributed to Black Carbon. Intense photochemical processing of high burn rate flaming combustion emissions in an oxidation flow reactor led to strong formation of Secondary Organic Aerosol, with no or weak absorption. PM1 mass emission factors (mg/kg) of fresh emissions were about an order of magnitude higher for low temperature pyrolysis compared to high temperature combustion. However, emission factors describing the absorption cross section emitted per kg of fuel consumed (m(2)/kg) were of similar magnitude at 520 nm for the diverse combustion conditions investigated in this study. These results provide a link between biomass combustion conditions, emitted particle types, and their optical properties in fresh and processed plumes which can be of value for source apportionment and balanced mitigation of biomass combustion emissions from a climate and health perspective.

  11. Absorption Coefficient, Molecular Composition, and Photodegradation of Different Types of Brown Carbon Aerosols

    NASA Astrophysics Data System (ADS)

    Lee, H. J.; Aiona, P. K.; Nizkorodov, S.; Laskin, J.; Laskin, A.

    2014-12-01

    Atmospheric aerosols that absorb solar radiation have a direct effect on climate. Brown carbon (BrC) represents the type of carbonaceous aerosols characterized by large absorption coefficients in the near-UV range of the spectrum. BrC can be either directly emitted into the atmosphere from combustion sources, or be formed in the atmosphere through multi-phase reactions, such as aging of secondary organic aerosols (SOA) mediated by ammonium sulfate (AS). Under the conditions of exposure to solar radiation, both primary and secondary BrC can potentially change their molecular composition and optical properties as a result of photodegradation of chromophoric compounds. This presentation will discuss the molecular level composition, the absorption and fluorescence spectra, and the mechanism of photodegradation among several representative types of BrC. The primary BrC samples include aerosol produced by smoldering wood combustion. The secondary BrC samples include AS aged products of chamber-generated SOA, products of reaction between methylglyoxal and AS, and SOA produced by the hogh-NOx photooxdiation of aromatic compounds, such as naphthalene. This presentation will also include preliminary data on the absorption and fluorescence spectra of photo-degraded bioaerosols. In all cases, absorption spectra of extracted bulk samples are measured during irradiation by a known flux of UV or visible light. The molecular level composition of the fresh and photobleached samples are characterized by high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). Photobleaching of BrC is found to occur over a range of atmospherically relevant time scales. In many cases, the molecular level composition of photobleached BrC exhibits only subtle changes suggesting that the optical and fluorescence properties of BrC are controlled by a few compounds present in low quantities. The observed fluorescence from non-biological BrC indicates potential issues in using fluorescence

  12. Spectral Light Absorption and Scattering by Aerosol Particles in Central Amazonia

    NASA Astrophysics Data System (ADS)

    Artaxo, P.; Holanda, B. A.; Ferreira De Brito, J.; Carbone, S.; Barbosa, H. M.; Rizzo, L. V.; Cirino, G. G.; Andreae, M. O.; Saturno, J.; Pöhlker, C.; Martin, S. T.; Holben, B. N.; Schafer, J.

    2015-12-01

    As part of the GoAmazon2014/5, a detailed characterization of spectral light absorption and light scattering was performed at four research sites located in the central Amazon forest at different distances upwind and downwind of Manaus. The sites ATTO (T0a) and Embrapa (T0e) are located upwind of Manaus where it is possible to observe very pristine atmospheric conditions in wet season. The site Tiwa (T2) is being operated under the direct influence of the Manaus plume at 5 km downwind of Manaus and, finally, the Manacapuru (T3) site is located at about 60 km downwind of Manaus. The spectral dependence of light absorption and light scattering were measured using Aethalometers (7-wavelengths) and Nephelometers (3-wavelengths), respectively. By calculating the Absorption Angstrom Exponent (AAE), it was possible to get information about the source of the aerosol whereas the Scattering Angstrom Exponent (SAE) gives information about its size distribution. Sunphotometers from the AERONET network were set up at T3 and T0e sites to measure column Aerosol Optical Depth (AOD). For all the stations, much higher absorption and scattering coefficients were observed during the dry season in comparison to the wet season, as a result of the larger concentration of BC and OC present in the biomass burning events. Additionally, we also observed Manaus plume pollution that alters the BC signal. There is also an increase of the AAE during the dry season due to the larger amount of aerosols from biomass burning compared with urban pollution. High values of AAE are also observed during the wet season, attributed to the presence of long-range transport of aerosols from Africa. The SAE for all the sites are lower during the wet season, with the dominance of large biological particles, and increases during the dry season as a consequence of fine particles emitted from both biomass and fossil fuel burning. The AOD at T0e and T3 (Jan-Jun/2014) showed very similar values ranging from 0.05 to

  13. Physical and Chemical Properties of Anthropogenic Aerosols: An overview

    EPA Science Inventory

    A wide variety of anthropogenic sources emit fine aerosols to the atmosphere. The physical and chemical properties of these aerosols are of interest due to their influence on climate, human health, and visibility. Aerosol chemical composition is complex. Combustion aerosols can c...

  14. A comprehensive climatology of Arctic aerosol properties on the North Slope of Alaska

    NASA Astrophysics Data System (ADS)

    Creamean, Jessie; de Boer, Gijs; Shupe, Matthew; McComiskey, Allison

    2016-04-01

    Evaluating aerosol properties has implications for the formation of Arctic clouds, resulting in impacts on cloud lifetime, precipitation processes, and radiative forcing. There are many remaining uncertainties and large discrepancies regarding modeled and observed Arctic aerosol properties, illustrating the need for more detailed observations to improve simulations of Arctic aerosol and more generally, projections of the components of the aerosol-driven processes that impact sea ice loss/gain. In particular, the sources and climatic effects of Arctic aerosol particles are severely understudied. Here, we present a comprehensive, long-term record of aerosol observations from the North Slope of Alaska baseline site at Barrow. These measurements include sub- and supermicron (up to 10 μm) total mass and number concentrations, sub- and supermicron soluble inorganic and organic ion concentrations, submicron metal concentrations, submicron particle size distributions, and sub- and supermicron absorption and scattering properties. Aerosol extinction and number concentration measurements extend back to 1976, while the remaining measurements were implemented since. Corroboration between the chemical, physical, and optical property measurements is evident during periods of overlapping observations, demonstrating the reliability of the measurements. During the Arctic Haze in the winter/spring, high concentrations of long-range transported submicron sea salt, mineral dust, industrial metals, pollution (non-sea salt sulfate, nitrate, ammonium), and biomass burning species are observed concurrent with higher concentrations of particles with sizes that span the submicron range, enhanced absorption and scattering coefficients, and largest Ångström exponents. The summer is characterized by high concentrations of small biogenic aerosols (< 100 nm) and low extinction coefficients. Fall is characterized by clean conditions, with supermicron sea salt representing the dominant aerosol

  15. Influences of external vs. core-shell mixing on aerosol optical properties at various relative humidities.

    PubMed

    Ramachandran, S; Srivastava, Rohit

    2013-05-01

    Aerosol optical properties of external and core-shell mixtures of aerosol species present in the atmosphere are calculated in this study for different relative humidities. Core-shell Mie calculations are performed using the values of radii, refractive indices and densities of aerosol species that act as core and shell, and the core-shell radius ratio. The single scattering albedo (SSA) is higher when the absorbing species (black carbon, BC) is the core, while for a sulfate core SSA does not vary significantly as the BC in the shell dominates the absorption. Absorption gets enhanced in core-shell mixing of absorbing and scattering aerosols when compared to their external mixture. Thus, SSA is significantly lower for a core-shell mixture than their external mixture. SSA is more sensitive to core-shell ratio than mode radius when BC is the core. The extinction coefficient, SSA and asymmetry parameter are higher for external mixing when compared to BC (core)-water soluble aerosol (shell), and water soluble aerosol (core)-BC (shell) mixtures in the relative humidity range of 0 to 90%. Spectral SSA exhibits the behaviour of the species which acts as a shell in core-shell mixing. The asymmetry parameter for an external mixture of water soluble aerosol and BC is higher than BC (core)-water soluble aerosol (shell) mixing and increases as function of relative humidity. The asymmetry parameter for the water soluble aerosol (core)-BC (shell) is independent of relative humidity as BC is hydrophobic. The asymmetry parameter of the core-shell mixture decreases when BC aerosols are involved in mixing, as the asymmetry parameter of BC is lower. Aerosol optical depth (AOD) of core-shell mixtures increases at a higher rate when the relative humidity exceeds 70% in continental clean and urban aerosol models, whereas AOD remains the same when the relative humidity exceeds 50% in maritime aerosol models. The SSA for continental aerosols varies for core-shell mixing of water soluble

  16. Multiwavelength In-Situ Aerosol Scattering and Absorption During the NEAQS-ITCT 2004 Field Campaign: Aerosol Classification, Case Studies, and Data Interpretation

    NASA Astrophysics Data System (ADS)

    Sierau, B.; Covert, D.; Coffman, D.; Quinn, P.; Bates, T.

    2005-12-01

    In-situ, three wavelength measurements of aerosol scattering and absorption of the New York and Boston urban pollution outflow were carried out aboard the NOAA research vessel Ronald H. Brown during the NEAQS-ITCT 2004 (New England Air Quality Study-Intercontinental Transport and Chemical Transformation Study) field campaign during July 2004 in the Gulf of Maine. Aerosol scattering, backscattering and absorption-coefficients were measured using integrating nephelometers and multiwavelength, filter-based absorption photometers (PSAPs) at ~55-60% RH (nephelometers). Two data sets were collected, one for particles with diameters dp<10μm and one for particles <1μm. The purpose of the latter was to focus on the largely pollution related accumulation mode and to minimize the uncertainty due to highly variable near-surface sea salt aerosol. Combining the aerosol scattering and absorption coefficients σsp and σap yields the derived, intensive parameters, single-scattering albedo, ω=σsp/(σsp+σap), Ångström exponents, å, for σsp, and σap, the hemispheric backscattering ratio, and the fine mode fraction of the aerosol, FMF =σsp(dp<1μm)/σsp(dp<10μm). These are key parameters in estimating aerosol direct radiative forcing and they provide constraints on model building and closure studies with physical and chemical aerosol properties. They are important for relating in-situ optical properties to those sensed remotely, e.g., optical depth from ground- or aircraft-based sun photometry or optical depth from satellite, and to the FMF retrieved from satellite data. The measured and derived data will be classified based on a trajectory analysis of the sampled air masses to identify distinct aerosol populations and sources. Case studies describing the aging of pollution plumes are calculated and analyzed in context of other measurements and the prevailing meteorology and the upwind sources. The obtained relationship between in-situ Ångström and FMF will be compared

  17. Method and apparatus for aerosol-particle absorption spectroscopy. [DOE patent application

    SciTech Connect

    Campillo, A.J.; Lin, H.B.

    1981-06-25

    A method and apparatus are described for determining the absorption spectra, and other properties, of aerosol particles. A heating beam source provides a beam of electromagnetic energy which is scanned through the region of the spectrum which is of interest. Particles exposed to the heating beam which have absorption bands within the band width of the heating beam absorb energy from the beam. The particles are also illuminated by light of a wave length such that the light is scattered by the particles. The absorption spectra of the particles can thus be determined from an analysis of the scattered light since the absorption of energy by the particles will affect the way the light is scattered. Preferably the heating beam is modulated to simplify the analysis of the scattered light. In one embodiment the heating beam is intensity modulated so that the scattered light will also be intensity modulated when the particles absorb energy. In another embodiment the heating beam passes through an interferometer and the scattered light reflects the Fourier Transform of the absorption spectra.

  18. Aerosol optical properties and radiative effects in the Yangtze Delta region of China

    NASA Astrophysics Data System (ADS)

    Xia, Xiangao; Li, Zhanqing; Holben, Brent; Wang, Pucai; Eck, Tom; Chen, Hongbin; Cribb, Maureen; Zhao, Yanxia

    2007-11-01

    One year's worth of aerosol and surface irradiance data from September 2005 to August 2006 were obtained at Taihu, the second supersite for the East Asian Study of Tropospheric Aerosols: An International Regional Experiment (EAST-AIRE). Aerosol optical properties derived from measurements by a Sun photometer were analyzed. The aerosol data were used together with surface irradiance data to quantitatively estimate aerosol effects on surface shortwave radiation (SWR) and photosynthetically active radiation (PAR). The annual mean aerosol optical depth at 500 nm is 0.77, and mean Ångstrom wavelength exponent is 1.17. The annual mean aerosol single scattering albedo and mean aerosol asymmetry factor at 440 nm are 0.90 and 0.72, respectively. Both parameters show a weak seasonal variation, with small values occurring during the winter and larger values during the summer. Clear positive relationships between relative humidity and aerosol properties suggest aerosol hygroscopic growth greatly modifies aerosol properties. The annual mean aerosol direct radiative forcing at the surface (ADRF) is -38.4 W m-2 and -17.8 W m-2 for SWR and PAR, respectively. Because of moderate absorption, the instantaneous ADRF at the top of the atmosphere derived from CERES SSF data is close to zero. Heavy aerosol loading in this region leads to -112.6 W m-2 and -45.5 W m-2 reduction in direct and global SWR, but 67.1 W m-2 more diffuse SWR reaching the surface. With regard to PAR, the annual mean differences in global, direct and diffuse irradiance are -23.1 W m-2, -65.2 W m-2 and 42.1 W m-2 with and without the presence of aerosol, respectively.

  19. Radiative Properties of Smoke and Aerosol Over Land Surfaces

    NASA Technical Reports Server (NTRS)

    King, Michael D.

    2000-01-01

    This talk discusses smoke and aerosol's radiative properties with particular attention to distinguishing the measurement over clear sky from clouds over land, sea, snow, etc. surfaces, using MODIS Airborne Simulator data from (Brazil, arctic sea ice and tundra and southern Africa, west Africa, and other ecosystems. This talk also discusses the surface bidirectional reflectance using Cloud Absorption Radiometer, BRDF measurements of Saudi Arabian desert, Persian Gulf, cerrado and rain forests in Brazil, sea ice, tundra, Atlantic Ocean, Great Dismal Swamp, Kuwait oil fire smoke. Recent upgrades to instrument (new TOMS UVA channels at 340 and 380 planned use in Africa (SAFARI 2000) and possibly for MEIDEX will also be discussed. This talk also plans to discuss the spectral variation of surface reflectance over land and the sensitivity of off-nadir view angles to correlation between visible near-infrared reflectance for use in remote sensing of aerosol over land.

  20. Systematic Relationships among Background SE U.S. Aerosol Optical, Micro-physical, and Chemical Properties-Development of an Optically-based Aerosol Characterization

    NASA Astrophysics Data System (ADS)

    Sherman, J. P.; Link, M. F.; Zhou, Y.

    2014-12-01

    Remote sensing-based retrievals of aerosol composition require known or assumed relationships between aerosol optical properties and types. Most optically-based aerosol classification schemes apply some combination of the spectral dependence of aerosol light scattering and absorption-using the absorption and either scattering or extinction Angstrom exponents (AAE, SAE and EAE), along with single-scattering albedo (SSA). These schemes can differentiate between such aerosol types as dust, biomass burning, and urban/industrial but no such studies have been conducted in the SE U.S., where a large fraction of the background aerosol is a variable mixture of biogenic SOA, sulfates, and black carbon. In addition, AERONET retrievals of SSA are often highly uncertain due to low AOD in the region during most months. The high-elevation, semi-rural AppalAIR facility at Appalachian State University in Boone, NC (1090m ASL, 36.210N, 81.690W) is home to the only co-located NOAA-ESRL and AERONET monitoring sites in the eastern U.S. Aerosol chemistry measured at AppalAIR is representative of the background SE U.S (Link et al. 2014) Dried aerosol light absorption and dried and humidified aerosol light scattering and hemispheric backscattering at 3 visible wavelengths and 2 particle size cuts (sub-1μm and sub-10μm) are measured continuously. Measurements of size-resolved, non-refractory sub-1μm aerosol composition were made by a co-located AMS during the 2012-2013 summers and 2013 winter. Systematic relationships among aerosol optical, microphysical, and chemical properties were developed to better understand aerosol sources and processes and for use in higher-dimension aerosol classification schemes. The hygroscopic dependence of visible light scattering is sensitive to the ratio of sulfate to organic aerosol(OA), as are SSA and AAE. SAE is a less sensitive indicator of fine-mode aerosol size than hemispheric backscatter fraction (b) and is more sensitive to fine-mode aerosol

  1. Optical and microphysical properties of atmospheric aerosols in Moldova

    NASA Astrophysics Data System (ADS)

    Aculinin, Alexandr; Smicov, Vladimir

    2010-05-01

    Measurements of aerosol properties in Kishinev, Moldova are being carried out within the framework of the international AERONET program managed by NASA/GSFC since 1999. Direct solar and sky diffuse radiances are measured by using of sunphotometer Cimel-318. Aerosol optical properties are retrieved from measured radiances by using of smart computational procedures developed by the AERONET's team. The instrument is situated at the ground-based solar radiation monitoring station giving the opportunity to make simultaneous spectral (win sunphotometer) and broadband (with the set of sensors from radiometric complex) solar radiation. Detailed description of the station and investigations in progress can be found at the http://arg.phys.asm.md. Ground station is placed in an urban environment of Kishinev city (47.00N; 28.56E; 205 m a.s.l). Summary of aerosol optical and microphysical properties retrieved from direct solar and diffuse sky radiance observations at Moldova site from September 1999 to June 2009 are presented below. Number of measurements (total): 1695 Number of measurements (for ?o, n, k): 223 Range of aerosol optical depth (AOD) @440 nm: 0.03 < ?(440) < 2.30, < ?(440)>=0.25 Range of Ångström parameter < α440_870 >: 0.14 < α < 2.28 Asymmetry factor (440/670/870/1020): 0.70/0.63/0.59/0.58 ±0.04 Refraction (n) and absorption (k) indices@440 nm: 1.41 ± 0.06; 0.009 ± 0.005 Single scattering albedo < ?o >(440/670/870/1020): 0.93/0.92/0.90/0.89 ±0.04 Parameters of volume particle size distribution function: (fine mode) volume median radius r v,f , μm: 0.17 ± 0.06 particle volume concentration Cv,f, μm3/μm2: 0.04 ± 0.03 (coarse mode) volume median radius rv,c , μm: 3.08 ± 0.64 particle volume concentration Cv,c, μm3/μm2: 0.03 ± 0.03 Climatic norms of AOD@500 nm and Ångström parameter < α440_870 > at the site of observation are equal to 0.21 ± 0.06 and 1.45 ± 0.14, respectively. The aerosol type in Moldova may be considered as 'urban

  2. Background Southeast United States Aerosol Optical Properties and Their Dependence Upon Meteorology

    NASA Astrophysics Data System (ADS)

    Pawlyszyn, C.; West, M.; Sherman, J. P.; Link, M.; Zhou, Y.

    2015-12-01

    Aerosol effects on SE U.S. radiation budget are highly-seasonal. Aerosol loading is much higher in summer, due largely to high levels of biogenic secondary organic aerosol and sulfates. Aerosol loading is lowest in winter. Aerosol optical properties relevant to radiative forcing have been measured continuously at the Appalachian Atmospheric Interdisciplinary Research facility (AppalAIR) since the summer of 2009. AppalAIR is the only site in the eastern US to house co-located NOAA ESRL and NASA AeroNET instrumentation and is located in the mountains of Boone, NC. Lower tropospheric sub-micron (PM1) light scattering and absorption coefficients measured over seven summers and six winters are presented here, in addition to PM1 organic and sulfate aerosol mass concentrations measured during summers 2012-2013 as well as winter 2013. The objective is to determine the influence of aerosol sources and meteorology along the air mass back-trajectories on aerosol loading and composition. PM1 aerosol mass was dominated by organic aerosol and sulfate during the periods measured. Aerosol light scattering and organic aerosol concentrations were positively correlated during summer with temperature and solar flux along the parcel back-trajectory and negatively-correlated with rainfall along the back-trajectory. Wet deposition was a major factor in the difference between the upper and lower scattering coefficient quartiles for both summer and winter. Summer PM1 light scattering coefficient declined by approximately 30-40% since 2009, with smaller decreases during winter months. Long-term studies of aerosol optical properties from the regionally-representative AppalAIR site are necessary to determine the relationships between changing SE U.S. air quality and aerosol effects on regional climate and weather.

  3. Aerosol Characterization and New Instrumentation for Better Understanding Snow Radiative Properties

    NASA Astrophysics Data System (ADS)

    Beres, N. D.

    2015-12-01

    Snow albedo is determined by snowpack thickness and grain size, but also affected by contamination with light-absorbing, microscopic (e.g., mineral dust, combustion aerosols, bio-aerosols) and macroscopic (e.g., microalgae, plant debris, sand, organisms) compounds. Most currently available instruments for measuring snow albedo utilize the natural, downward flux of solar radiation and the reflected upward flux. This reliance on solar radiation (and, thus, large zenith angles and clear-sky conditions) leads to severe constraints, preventing characterization of detailed diurnal snow albedo cycles. Here, we describe instrumentation and methodologies to address these limitations with the development and deployment of new snow radiation sensors for measuring surface spectral and in-snow radiative properties. This novel instrumentation will be tested at the CRREL/UCSB Eastern Sierra (CUES) Snow Study Site at Mammoth Mountain, which is extensively instrumented for characterizing snow properties including snow albedo and surface morphology. However, it has been lacking instrumentation for the characterization of aerosols that can be deposited on the snow surface through dry and wet deposition. Currently, we are installing aerosol instrumentation at the CUES site, which are also described. This includes instruments for the multi-wavelength measurement of aerosol scattering and absorption coefficients and for the characterization of aerosol size distribution. Knowledge of aerosol concentration and physical and optical properties will allow for the study of aerosol deposition and modification of snow albedo and for establishing an aerosol climatology for the CUES site.

  4. Use of the NASA GEOS-5 SEAC4RS Meteorological and Aerosol Reanalysis for assessing simulated aerosol optical properties as a function of smoke age

    NASA Astrophysics Data System (ADS)

    Randles, C. A.; da Silva, A. M., Jr.; Colarco, P. R.; Darmenov, A.; Buchard, V.; Govindaraju, R.; Chen, G.; Hair, J. W.; Russell, P. B.; Shinozuka, Y.; Wagner, N.; Lack, D.

    2014-12-01

    The NASA Goddard Earth Observing System version 5 (GEOS-5) Earth system model, which includes an online aerosol module, provided chemical and weather forecasts during the SEAC4RS field campaign. For post-mission analysis, we have produced a high resolution (25 km) meteorological and aerosol reanalysis for the entire campaign period. In addition to the full meteorological observing system used for routine NWP, we assimilate 550 nm aerosol optical depth (AOD) derived from MODIS (both Aqua and Terra satellites), ground-based AERONET sun photometers, and the MISR instrument (over bright surfaces only). Daily biomass burning emissions of CO, CO2, SO2, and aerosols are derived from MODIS fire radiative power retrievals. We have also introduced novel smoke "age" tracers, which provide, for a given time, a snapshot histogram of the age of simulated smoke aerosol. Because GEOS-5 assimilates remotely sensed AOD data, it generally reproduces observed (column) AOD compared to, for example, the airborne 4-STAR instrument. Constraining AOD, however, does not imply a good representation of either the vertical profile or the aerosol microphysical properties (e.g., composition, absorption). We do find a reasonable vertical structure for aerosols is attained in the model, provided actual smoke injection heights are not much above the planetary boundary layer, as verified with observations from DIAL/HRSL aboard the DC8. The translation of the simulated aerosol microphysical properties to total column AOD, needed in the aerosol assimilation step, is based on prescribed mass extinction efficiencies that depend on wavelength, composition, and relative humidity. Here we also evaluate the performance of the simulated aerosol speciation by examining in situ retrievals of aerosol absorption/single scattering albedo and scattering growth factor (f(RH)) from the LARGE and AOP suite of instruments. Putting these comparisons in the context of smoke age as diagnosed by the model helps us to

  5. The impact of biogenic carbon emissions on aerosol absorption inMexico City

    SciTech Connect

    Marley, N; Gaffney, J; Tackett, M J; Sturchio, N; Hearty, L; Martinez, N; Hardy, K D; Machany-Rivera, A; Guilderson, T P; MacMillan, A; Steelman, K

    2009-02-24

    In order to determine the wavelength dependence of atmospheric aerosol absorption in the Mexico City area, the absorption angstrom exponents (AAEs) were calculated from aerosol absorption measurements at seven wavelengths obtained with a seven-channel aethalometer during two field campaigns, the Mexico City Metropolitan Area study in April 2003 (MCMA 2003) and the Megacity Initiative: Local and Global Research Observations in March 2006 (MILAGRO). The AAEs varied from 0.76 to 1.56 in 2003 and from 0.54 to 1.52 in 2006. The AAE values determined in the afternoon were consistently higher than the corresponding morning values, suggesting the photochemical formation of absorbing secondary organic aerosols (SOA) in the afternoon. The AAE values were compared to stable and radiocarbon isotopic measurements of aerosol samples collected at the same time to determine the sources of the aerosol carbon. The fraction of modern carbon (fM) in the aerosol samples, as determined from {sup 14}C analysis, showed that 70% of the carbonaceous aerosols in Mexico City were from modern sources, indicating a significant impact from biomass burning during both field campaigns. The {sup 13}C/{sup 12}C ratios of the aerosol samples illustrate the significant impact of Yucatan forest fires (C-3 plants) in 2003 and local grass fires (C-4 plants) at site T1 in 2006. A direct comparison of the fM values, stable carbon isotope ratios, and calculated aerosol AAEs suggested that the wavelength dependence of the aerosol absorption was controlled by the biogenically derived aerosol components.

  6. Analysis of functional groups in atmospheric aerosols by infrared spectroscopy: sparse methods for statistical selection of relevant absorption bands

    NASA Astrophysics Data System (ADS)

    Takahama, Satoshi; Ruggeri, Giulia; Dillner, Ann M.

    2016-07-01

    Various vibrational modes present in molecular mixtures of laboratory and atmospheric aerosols give rise to complex Fourier transform infrared (FT-IR) absorption spectra. Such spectra can be chemically informative, but they often require sophisticated algorithms for quantitative characterization of aerosol composition. Naïve statistical calibration models developed for quantification employ the full suite of wavenumbers available from a set of spectra, leading to loss of mechanistic interpretation between chemical composition and the resulting changes in absorption patterns that underpin their predictive capability. Using sparse representations of the same set of spectra, alternative calibration models can be built in which only a select group of absorption bands are used to make quantitative prediction of various aerosol properties. Such models are desirable as they allow us to relate predicted properties to their underlying molecular structure. In this work, we present an evaluation of four algorithms for achieving sparsity in FT-IR spectroscopy calibration models. Sparse calibration models exclude unnecessary wavenumbers from infrared spectra during the model building process, permitting identification and evaluation of the most relevant vibrational modes of molecules in complex aerosol mixtures required to make quantitative predictions of various measures of aerosol composition. We study two types of models: one which predicts alcohol COH, carboxylic COH, alkane CH, and carbonyl CO functional group (FG) abundances in ambient samples based on laboratory calibration standards and another which predicts thermal optical reflectance (TOR) organic carbon (OC) and elemental carbon (EC) mass in new ambient samples by direct calibration of infrared spectra to a set of ambient samples reserved for calibration. We describe the development and selection of each calibration model and evaluate the effect of sparsity on prediction performance. Finally, we ascribe

  7. Solar Absorption by Aerosol-Bound Nitrophenols Compared to Aqueous and Gaseous Nitrophenols.

    PubMed

    Hinrichs, Ryan Z; Buczek, Pawel; Trivedi, Jal J

    2016-06-01

    Nitrophenols are well-known absorbers of near-UV/blue radiation and are considered to be a component of solar-absorbing organic aerosol material commonly labeled brown carbon. Nitrophenols have been identified in a variety of phases in earth's atmosphere, including the gaseous, aqueous, and aerosol bound, and these different environments alter their UV-vis absorption spectra, most dramatically when deprotonated forming nitrophenolates. We quantify the impact of these different absorption profiles by calculating the solar power absorbed per molecule for several nitrophenols. For instance, aqueous 2,4-dinitrophenol absorption varies dramatically over the pH range of cloud droplets with pH = 5.5 solutions absorbing three times the solar power compared to pH = 3.5 solutions. We also measured the UV-vis spectra of 2-nitrophenol adsorbed on several aerosol substrates representative of mineral dust, inorganic salts, and organic aerosol and compare these spectra to gaseous and aqueous 2-nitrophenol. 2-Nitrophenol adsorbed on mineral and chloride aerosol substrates exhibits a red-shifted absorption band (∼450-650 nm) consistent with 2-nitrophenolate and absorbs twice the solar power per molecule compared to gaseous, aqueous, and organic aerosol-bound 2-nitrophenol. We also discuss how different nitrophenol absorption profiles alter important atmospheric photolysis rate constants [e.g., J(NO2) and J(O3)] by attenuating solar flux.

  8. Influence of the vertical absorption profile of mixed Asian dust plumes on aerosol direct radiative forcing over East Asia

    NASA Astrophysics Data System (ADS)

    Noh, Young Min; Lee, Kwonho; Kim, Kwanchul; Shin, Sung-Kyun; Müller, Detlef; Shin, Dong Ho

    2016-08-01

    We estimate the aerosol direct radiative forcing (ADRF) and heating rate profiles of mixed East Asian dust plumes in the solar wavelength region ranging from 0.25 to 4.0 μm using the Santa Barbara Discrete Ordinate Atmospheric Radiative Transfer (SBDART) code. Vertical profiles of aerosol extinction coefficients and single-scattering albedos (SSA) were derived from measurements with a multi-wavelength Raman lidar system. The data are used as input parameters for our radiative transfer calculations. We considered four cases of radiative forcing in SBDART: 1. dust, 2. pollution, 3. mixed dust plume and the use of vertical profiles of SSA, and 4. mixed dust plumes and the use of column-averaged values of SSA. In our sensitivity study we examined the influence of SSA and aerosol layer height on our results. The ADRF at the surface and in the atmosphere shows a small dependence on the specific shape of the aerosol extinction vertical profile and its light-absorption property for all four cases. In contrast, at the top of the atmosphere (TOA), the ADRF is largely affected by the vertical distribution of the aerosols extinction. This effect increases if the light-absorption capacity (decrease of SSA) of the aerosols increases. We find different radiative effects in situations in which two layers of aerosols had different light-absorption properties. The largest difference was observed at the TOA for an absorbing aerosol layer at high altitude in which we considered in one case the vertical profile of SSA and in another case the column-averaged SSA only. The ADRF at the TOA increases when the light-absorbing aerosol layer is located above 3 km altitude. The differences between height-resolved SSA, which can be obtained from lidar data, and total layer-mean SSA indicates that the use of a layer-mean SSA can be rather misleading as it can induce a large error in the calculation of the ADRF at the TOA, which in turn may cause errors in the vertical profiles of heating rates.

  9. AeroCom INSITU Project: Comparison of Aerosol Optical Properties from In-situ Surface Measurements and Model Simulations

    NASA Astrophysics Data System (ADS)

    Schmeisser, L.; Andrews, E.; Schulz, M.; Fiebig, M.; Zhang, K.; Randles, C. A.; Myhre, G.; Chin, M.; Stier, P.; Takemura, T.; Krol, M. C.; Bian, H.; Skeie, R. B.; da Silva, A. M., Jr.; Kokkola, H.; Laakso, A.; Ghan, S.; Easter, R. C.

    2015-12-01

    AeroCom, an open international collaboration of scientists seeking to improve global aerosol models, recently initiated a project comparing model output to in-situ, surface-based measurements of aerosol optical properties. The model/measurement comparison project, called INSITU, aims to evaluate the performance of a suite of AeroCom aerosol models with site-specific observational data in order to inform iterative improvements to model aerosol modules. Surface in-situ data have the unique property of being traceable to physical standards, which is a big asset in accomplishing the overarching goal of bettering the accuracy of aerosol processes and predicative capability of global climate models. The INSITU project looks at how well models reproduce aerosol climatologies on a variety of time scales, aerosol characteristics and behaviors (e.g., aerosol persistence and the systematic relationships between aerosol optical properties), and aerosol trends. Though INSITU is a multi-year endeavor, preliminary phases of the analysis, using GOCART and other models participating in this AeroCom project, show substantial model biases in absorption and scattering coefficients compared to surface measurements, though the sign and magnitude of the bias varies with location and optical property. Spatial patterns in the biases highlight model weaknesses, e.g., the inability of models to properly simulate aerosol characteristics at sites with complex topography (see Figure 1). Additionally, differences in modeled and measured systematic variability of aerosol optical properties suggest that some models are not accurately capturing specific aerosol co-dependencies, for example, the tendency of in-situ surface single scattering albedo to decrease with decreasing aerosol extinction coefficient. This study elucidates specific problems with current aerosol models and suggests additional model runs and perturbations that could further evaluate the discrepancies between measured and modeled

  10. Impact of Nonabsorbing Anthropogenic Aerosols on Clear-Sky Atmospheric Absorption

    NASA Technical Reports Server (NTRS)

    Stier, Philip; Seinfeld, John H.; Kinne, Stefan; Feichter,Johann; Boucher, Olivier

    2006-01-01

    Absorption of solar radiation by atmospheric aerosol has become recognized as important in regional and global climate. Nonabsorbing, hydrophilic aerosols, such as sulfate, potentially affect atmospheric absorption in opposing ways: first, decreasing absorption through aging initially hydrophobic black carbon (BC) to a hydrophilic state, enhancing its removal by wet scavenging, and consequently decreasing BC lifetime and abundance, and second, increasing absorption through enhancement of the BC absorption efficiency by internal mixing as well as through increasing the amount of diffuse solar radiation in the atmosphere. On the basis of General Circulation Model studies with an embedded microphysical aerosol module we systematically demonstrate the significance of these mechanisms both on the global and regional scales. In remote transport regions, the first mechanism prevails, reducing atmospheric absorption, whereas in the vicinity of source regions, despite enhanced wet scavenging, absorption is enhanced owing to the prevalence of the second mechanisms. Our findings imply that the sulfur to BC emission ratio plays a key role in aerosol absorption.

  11. Vertical distribution of aerosol optical properties based on aircraft measurements over the Loess Plateau in China.

    PubMed

    Li, Junxia; Liu, Xingang; Yuan, Liang; Yin, Yan; Li, Zhanqing; Li, Peiren; Ren, Gang; Jin, Lijun; Li, Runjun; Dong, Zipeng; Li, Yiyu; Yang, Junmei

    2015-08-01

    Vertical distributions of aerosol optical properties based on aircraft measurements over the Loess Plateau were measured for the first time during a summertime aircraft campaign, 2013 in Shanxi, China. Data from four flights were analyzed. The vertical distributions of aerosol optical properties including aerosol scattering coefficients (σsc), absorption coefficients (σab), Angström exponent (α), single scattering albedo (ω), backscattering ratio (βsc), aerosol mass scattering proficiency (Qsc) and aerosol surface scattering proficiency (Qsc(')) were obtained. The mean statistical values of σsc were 77.45 Mm(-1) (at 450 nm), 50.72 Mm(-1) (at 550n m), and 32.02 Mm(-1) (at 700 nm). The mean value of σab was 7.62 Mm(-1) (at 550 nm). The mean values of α, βsc and ω were 1.93, 0.15, and 0.91, respectively. Aerosol concentration decreased with altitude. Most effective diameters (ED) of aerosols were less than 0.8 μm. The vertical profiles of σsc,, α, βsc, Qsc and Qsc(') showed that the aerosol scattering properties at lower levels contributed the most to the total aerosol radiative forcing. Both α and βsc had relatively large values, suggesting that most aerosols in the observational region were small particles. The mean values of σsc, α, βsc, Qsc, Qsc('), σab and ω at different height ranges showed that most of the parameters decreased with altitude. The forty-eight hour backward trajectories of air masses during the observation days indicated that the majority of aerosols in the lower level contributed the most to the total aerosol loading, and most of these particles originated from local or regional pollution emissions.

  12. Case study of modeled aerosol optical properties during the SAFARI 2000 campaign.

    PubMed

    Kuzmanoski, Maja; Box, Michael A; Schmid, Beat; Russell, Philip B; Redemann, Jens

    2007-08-01

    We present modeled aerosol optical properties (single scattering albedo, asymmetry parameter, and lidar ratio) in two layers with different aerosol loadings and particle sizes, observed during the Southern African Regional Science Initiative 2,000 (SAFARI 2,000) campaign. The optical properties were calculated from aerosol size distributions retrieved from aerosol layer optical thickness spectra, measured using the NASA Ames airborne tracking 14-channel sunphotometer (AATS-14) and the refractive index based on the available information on aerosol chemical composition. The study focuses on sensitivity of modeled optical properties in the 0.3-1.5 microm wavelength range to assumptions regarding the mixing scenario. We considered two models for the mixture of absorbing and nonabsorbing aerosol components commonly used to model optical properties of biomass burning aerosol: a layered sphere with absorbing core and nonabsorbing shell and the Maxwell-Garnett effective medium model. In addition, comparisons of modeled optical properties with the measurements are discussed. We also estimated the radiative effect of the difference in aerosol absorption implied by the large difference between the single scattering albedo values (approximately 0.1 at midvisible wavelengths) obtained from different measurement methods for the case with a high amount of biomass burning particles. For that purpose, the volume fraction of black carbon was varied to obtain a range of single scattering albedo values (0.81-0.91 at lambda=0.50 microm). The difference in absorption resulted in a significant difference in the instantaneous radiative forcing at the surface and the top of the atmosphere (TOA) and can result in a change of the sign of the aerosol forcing at TOA from negative to positive.

  13. Climatological Aspects of the Optical Properties of Fine/Coarse Mode Aerosol Mixtures

    NASA Technical Reports Server (NTRS)

    Eck, T. F.; Holben, B. N.; Sinyuk, A.; Pinker, R. T.; Goloub, P.; Chen, H.; Chatenet, B.; Li, Z.; Singh, R. P.; Tripathi, S.N.; Reid, J. S.; Giles, D. M.; Dubovik O.; O'Neill, N. T.; Smirnov, A.; Wang, P.; Xia, X.

    2010-01-01

    Aerosol mixtures composed of coarse mode desert dust combined with fine mode combustion generated aerosols (from fossil fuel and biomass burning sources) were investigated at three locations that are in and/or downwind of major global aerosol emission source regions. Multiyear monitoring data at Aerosol Robotic Network sites in Beijing (central eastern China), Kanpur (Indo-Gangetic Plain, northern India), and Ilorin (Nigeria, Sudanian zone of West Africa) were utilized to study the climatological characteristics of aerosol optical properties. Multiyear climatological averages of spectral single scattering albedo (SSA) versus fine mode fraction (FMF) of aerosol optical depth at 675 nm at all three sites exhibited relatively linear trends up to 50% FMF. This suggests the possibility that external linear mixing of both fine and coarse mode components (weighted by FMF) dominates the SSA variation, where the SSA of each component remains relatively constant for this range of FMF only. However, it is likely that a combination of other factors is also involved in determining the dynamics of SSA as a function of FMF, such as fine mode particles adhering to coarse mode dust. The spectral variation of the climatological averaged aerosol absorption optical depth (AAOD) was nearly linear in logarithmic coordinates over the wavelength range of 440-870 nm for both the Kanpur and Ilorin sites. However, at two sites in China (Beijing and Xianghe), a distinct nonlinearity in spectral AAOD in logarithmic space was observed, suggesting the possibility of anomalously strong absorption in coarse mode aerosols increasing the 870 nm AAOD.

  14. Aerosol optical properties in the Marine Environment during the TCAP-I campaign

    NASA Astrophysics Data System (ADS)

    Chand, D.; Berg, L. K.; Barnard, J.; Berkowitz, C. M.; Burton, S. P.; Chapman, E. G.; Comstock, J. M.; Fast, J. D.; Ferrare, R. A.; Connor, F. J.; Hair, J. W.; Hostetler, C. A.; Hubbe, J.; Kluzek, C.; Mei, F.; Pekour, M. S.; Sedlacek, A. J.; Schmid, B.; Shilling, J. E.; Shinozuka, Y.; Tomlinson, J. M.; Wilson, J. M.; Zelenyuk-Imre, A.

    2013-12-01

    The role of direct radiative forcing by atmospheric aerosol is one of the largest sources of uncertainty in predicting climate change. Much of this uncertainty comes from the limited knowledge of observed aerosol optical properties. In this presentation we discuss derived aerosol optical properties based on measurements made during the summer 2012 Two-Column Aerosol Project-I (TCAP) campaign and relate these properties to the corresponding chemical and physical properties of the aerosol. TCAP was designed to provide simultaneous, in-situ observations of the size distribution, chemical properties, and optical properties of aerosol within and between two atmospheric columns over the Atlantic Ocean near the eastern seaboard of the United States. These columns are separated by 200-300 km and were sampled in July 2012 during a summer intensive operation period (IOP) using the U.S. Department of Energy's Gulfstream-1 (G-1) and NASA's B200 aircraft, winter IOP using G-1 aircraft in February 2013, and the surface-based DOE Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) located on Cape Cod. In this presentation we examine the spectral dependence of the aerosol optical properties measured from the aircraft over the TCAP-I domain, with an emphasis on in-situ derived intensive properties measured by a 3-λ Nephelometer, a Particle Soot Absorption Photometer (PSAP), a humidograph (f(RH)), and a Single Particle Soot Photometer (SP2). Preliminary results indicate that the aerosol are more light-absorbing as well as more hygroscopic at higher altitudes (2-4 km) compared to the corresponding values made within residual layers near the surface (0-2 km altitude). The average column (0-4 km) single scattering albedo (ω) and hygroscopic scattering factor (F) are found to be ~0.96 and 1.25, respectively. Additional results on key aerosol intensive properties such as the angstrom exponent (å), asymmetry parameter (g), backscattering fraction (b), and gamma parameter (

  15. Aerosol ultraviolet absorption experiment (2002 to 2004), part 2: absorption optical thickness, refractive index, and single scattering albedo

    NASA Astrophysics Data System (ADS)

    Krotkov, Nickolay A.; Bhartia, Pawan K.; Herman, Jay R.; Slusser, James R.; Scott, Gwendolyn R.; Labow, Gordon J.; Vasilkov, Alexander P.; Eck, Tom; Doubovik, Oleg; Holben, Brent N.

    2005-04-01

    Compared to the visible spectral region, very little is known about aerosol absorption in the UV. Without such information it is impossible to quantify the causes of the observed discrepancy between modeled and measured UV irradiances and photolysis rates. We report results of a 17-month aerosol column absorption monitoring experiment conducted in Greenbelt, Maryland, where the imaginary part of effective refractive index k was inferred from the measurements of direct and diffuse atmospheric transmittances by a UV-multifilter rotating shadowband radiometer [UV-MFRSR, U.S. Department of Agriculture (USDA) UV-B Monitoring and Research Network]. Colocated ancillary measurements of aerosol effective particle size distribution and refractive index in the visible wavelengths [by CIMEL sun-sky radiometers, National Aeronautics and Space Administration (NASA) Aerosol Robotic Network (AERONET)], column ozone, surface pressure, and albedo constrain the forward radiative transfer model input, so that a unique solution for k is obtained independently in each UV-MFRSR spectral channel. Inferred values of k are systematically larger in the UV than in the visible wavelengths. The inferred k values enable calculation of the single scattering albedo ω, which is compared with AERONET inversions in the visible wavelengths. On cloud-free days with high aerosol loadings [τext(440)>0.4], ω is systematically lower at 368 nm (<ω368>=0.94) than at 440 nm (<ω440>=0.96), however, the mean ω differences (0.02) are within expected uncertainties of ω retrievals (~0.03). The inferred ω is even lower at shorter UV wavelengths (<ω325>~<ω332>=0.92), which might suggest the presence of selectively UV absorbing aerosols. We also find that decreases with decrease in aerosol loading. This could be due to real changes in the average aerosol composition between summer and winter months at the Goddard Space Flight Center (GSFC) site.

  16. Morphology and Optical Properties of Mixed Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Fard, Mehrnoush M.; Krieger, Ulrich; Rudich, Yinon; Marcolli, Claudia; Peter, Thomas

    2016-04-01

    Experiments and modeling studies have shown that deliquesced aerosols can exist not only as one-phase system containing organics, inorganic salts and water, but often as two-phase systems consisting of a predominantly organic and a predominantly inorganic aqueous phase (1,2). Recent laboratory studies conducted with model mixtures representing tropospheric aerosols (1,2,3), secondary organic aerosol (SOA) from smog chamber experiments (4), and field measurements (5) suggest that liquid-liquid phase separations (LLPS) is indeed a common phenomenon in mixed organic/ inorganic particles. During LLPS, particles may adopt different morphologies mainly core-shell and partially engulfed. A core-shell configuration will have consequences for heterogeneous chemistry and hygroscopicity and as a result will alter the optical properties of the particles in particular for organic phases containing absorbing molecules, e.g. brown carbon. The primary objective of this project is to establish a method for investigating the morphology of mixed inorganic and absorbing organic compounds of atmospheric relevance and study their radiative properties before, during, and after phase transitions mainly during LLPS. This will be the first study looking into the radiative effect of LLPS in detail. Our ternary model system consist of ammonium sulfate (AS)/ Polyethylene Glycol (PEG)/ and water (H2O). Carminic acid (CA) was added as a proxy for an absorbing organic compound to the system. The behavior of single droplets of above ternary mixture was monitored during relative humidity (RH) cycles using optical microscopy. The same ternary mixture particle was levitated in an electrodynamic balance (EDB) and the change in its absorption properties was measured at varying RH. In addition, Mie-code modeling is used to predict the absorption efficiency of the same ternary system and the result will be compared with the data obtained from EDB experiment. We also intend to determine the occurrence of

  17. Improved aerosol radiative properties as a foundation for solar geoengineering risk assessment

    NASA Astrophysics Data System (ADS)

    Dykema, J. A.; Keith, D. W.; Keutsch, F. N.

    2016-07-01

    Side effects resulting from the deliberate injection of sulfate aerosols intended to partially offset climate change have motivated the investigation of alternatives, including solid aerosol materials. Sulfate aerosols warm the tropical tropopause layer, increasing the flux of water vapor into the stratosphere, accelerating ozone loss, and increasing radiative forcing. The high refractive index of some solid materials may lead to reduction in these risks. We present a new analysis of the scattering efficiency and absorption of a range of candidate solid aerosols. We utilize a comprehensive radiative transfer model driven by updated, physically consistent estimates of optical properties. We compute the potential increase in stratospheric water vapor and associated longwave radiative forcing. We find that the stratospheric heating calculated in this analysis indicates some materials to be substantially riskier than previous work. We also find that there are Earth-abundant materials that may reduce some principal known risks relative to sulfate aerosols.

  18. Toward Creating A Global Retrospective Climatology of Aerosol Properties

    NASA Technical Reports Server (NTRS)

    Curran, Robert J.; Mishchenko, Michael I.; Hansen, James E. (Technical Monitor)

    2000-01-01

    Tropospheric aerosols are thought to cause a significant direct and indirect climate forcing, but the magnitude of this forcing remains highly uncertain because of poor knowledge of global aerosol characteristics and their temporal changes. The standard long-term global product, the one-channel Advanced Very-High-Resolution Radiometer (AVHRR) aerosol optical thickness over the ocean, relies on a single predefined aerosol model and can be inaccurate in many cases. Furthermore, it provides no information on aerosol column number density, thus making it impossible to estimate the indirect aerosol effect on climate. Total Ozone Mapping Spectrometer (TOMS) data can be used to detect absorbing aerosols over land, but are insensitive to aerosols located below one kilometer. It is thus clear that innovative approaches must be employed in order to extract a more quantitative and accurate aerosol climatology from available satellite and other measurements, thus enabling more reliable estimates of the direct and indirect aerosol forcings. The Global Aerosol Climatology Project (GACP) was established in 1998 as part of the Global Energy and Water Cycle Experiment (GEWEX). Its main objective is to analyze satellite radiance measurements and field observations to infer the global distribution of aerosols, their properties, and their seasonal and interannual variations. The overall goal is to develop advanced global aerosol climatologies for the period of satellite data and to make the aerosol climatologies broadly available through the GACP web site.

  19. Aerosol properties and associated radiative effects over Cairo (Egypt)

    NASA Astrophysics Data System (ADS)

    El-Metwally, M.; Alfaro, S. C.; Wahab, M. M. Abdel; Favez, O.; Mohamed, Z.; Chatenet, B.

    2011-02-01

    Cairo is one of the largest megacities in the World and the particle load of its atmosphere is known to be particularly important. In this work we aim at assessing the temporal variability of the aerosol's characteristics and the magnitude of its impacts on the transfer of solar radiation. For this we use the level 2 quality assured products obtained by inversion of the instantaneous AERONET sunphotometer measurements performed in Cairo during the Cairo Aerosol CHaracterization Experiment (CACHE), which lasted from the end of October 2004 to the end of March 2006. The analysis of the temporal variation of the aerosol's optical depth (AOD) and spectral dependence suggests that the aerosol is generally a mixture of at least 3 main components differing in composition and size. This is confirmed by the detailed analysis of the monthly-averaged size distributions and associated optical properties (single scattering albedo and asymmetry parameter). The components of the aerosol are found to be 1) a highly absorbing background aerosol produced by daily activities (traffic, industry), 2) an additional, 'pollution' component produced by the burning of agricultural wastes in the Nile delta, and 3) a coarse desert dust component. In July, an enhancement of the accumulation mode is observed due to the atmospheric stability favoring its building up and possibly to secondary aerosols being produced by active photochemistry. More generally, the time variability of the aerosol's characteristics is due to the combined effects of meteorological factors and seasonal production processes. Because of the large values of the AOD achieved during the desert dust and biomass burning episodes, the instantaneous aerosol radiative forcing (RF) at both the top (TOA) and bottom (BOA) of the atmosphere is maximal during these events. For instance, during the desert dust storm of April 8, 2005 RF BOA, RF TOA, and the corresponding atmospheric heating rate peaked at - 161.7 W/m 2, - 65.8 W/m 2

  20. Demonstration of the Applicability of Novel Photoacoustic Aerosol Monitor for Optical Absorption Coefficient Determination. Laboratory and Field Test.

    NASA Astrophysics Data System (ADS)

    Ajtai, T.; Schnaiter, M.; Linke, C.; Vragel, M.; Filep, Á.; Fődi, L.; Motika, G.; Bozóki, Z.; Szabó, G.

    2009-04-01

    Despite of its importance, the possibilities to determine the direct radiative forcing by atmospheric aerosols is very limited due to lack of the reliable on-line instruments. Therefore there is an increasing concern for novel methods promising more accurate and reliable results in this field. The accuracy and reliability of the available on-line instruments like SP2 (Single Particle Soot Photometer), MAAP (Multi Angle Absorption Photometer), are limited by the weakness of the spectral resolution or the sampling artefact of filter matrix during the light attenuation measurement on the deposited filter. These methods neither suitable for direct determination of the light absorption by aerosols nor dispose the capability of the source apportionment. In this work we present a novel photoacoustic based instrument for direct light absorption measurements in the atmosphere and demonstrate the suitability of that both in laboratory and field circumstances. We have developed a novel Multi Wavelength PhotoAcoustic System (WaSul-MuWaPas) based on the diode laser pumped, high repetition rate, Q-switched Nd:YAG laser and its frequency converted harmonics for direct determination of light absorption by aerosols. This instrument has designed to make in situ measurements at four different wavelengths simultaneously from the NIR to the UV wavelength range (1064nm, 532nm, 355nm, 266nm). The Wasul-MuWaPas measures directly the optical absorption coefficient on airborne particles, not belong to the integrated plate type technique (filter-free operation), operating at wide wavelength range (source apportionment possibilities), due to the possibilities of the wavelength independent cell constant determination the measurement method is absolute. Because of these the Wasul-MuWaPas system may become one of the best candidate for absorption measurements of various atmospheric aerosols such as black carbon, mineral dust, and secondary organic and inorganic aerosols as well as for source

  1. An AeroCom Initial Assessment - Optical Properties in Aerosol Component Modules of Global Models

    SciTech Connect

    Kinne, Stefan; Schulz, M.; Textor, C.; Guibert, S.; Balkanski, Y.; Bauer, S.; Berntsen, T.; Berglen, T.; Boucher, Olivier; Chin, M.; Collins, W.; Dentener, F.; Diehl, T.; Easter, Richard C.; Feichter, H.; Fillmore, D.; Ghan, Steven J.; Ginoux, P.; Gong, S.; Grini, A.; Hendricks, J.; Herzog, M.; Horrowitz, L.; Isaksen, I.; Iversen, T.; Kirkevag, A.; Kloster, S.; Koch, D.; Kristjansson, J. E.; Krol, M.; Lauer, A.; Lamarque, J. F.; Lesins, G.; Liu, Xiaohong; Lohmann, U.; Montanaro, V.; Myhre, G.; Penner, Joyce E.; Pitari, G.; Reddy, S.; Seland, O.; Stier, P.; Takemura, T.; Tie, X.

    2006-05-29

    The AeroCom exercise diagnoses multi-component aerosol modules in global modeling. In an initial assessment global fields for mass and for mid-visible aerosol optical thickness (aot) were compared among aerosol component modules of 21 different global models. There is general agreement among models for the annual global mean of component combined aot. At 0.12 to 0.14, simulated aot values are at the lower end of global averages suggested by remote sensing from ground (AERONET ca 0.14) and space (MODIS-MISR composite ca 0.16). More detailed comparisons, however, reveal that larger differences in regional distribution and significant differences in compositional mixture have remained. Of particular concern is the large model diversity for contributions by dust and carbon, because it leads to significant uncertainty in aerosol absorption (aab). Since not only aot but also aab influence the aerosol impact on the radiative energy-balance, aerosol (direct) forcing uncertainty in modeling is larger than differences in aot might suggest. New diagnostic approaches are proposed to trace model differences in terms of aerosol processing and transport: These include the prescription of common input (e.g. amount, size and injection of aerosol component emissions) and the use of observational capabilities from ground (e.g. measurements networks) and space (e.g. correlations between retrieved aerosol and cloud properties).

  2. Light Absorption of Brown Carbon Aerosol in the Pearl River Delta Region of China

    NASA Astrophysics Data System (ADS)

    Huang, X.

    2015-12-01

    X.F. Huang, J.F. Yuan, L.M. Cao, J. Cui, C.N. Huang, Z.J. Lan and L.Y. He Key Laboratory for Urban Habitat Environmental Science and Technology, School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen 518055, ChinaCorresponding author. Tel.: +86 755 26032532; fax: +86 755 26035332. E-mail address: huangxf@pku.edu.cn (X. F. Huang). Abstract: The strong spectral dependence of light absorption of brown carbon (BrC) aerosol has been recognized in recent decades. The Absorption Angstrom Exponent (AAE) of ambient aerosol was widely used in previous studies to attribute light absorption of brown carbon at shorter wavelengths, with a theoretical assumption that the AAE of black carbon (BC) aerosol equals to unit. In this study, the AAE method was improved by statistical extrapolation based on ambient measurements in the polluted seasons in typical urban and rural areas in the Pearl River Delta (PRD) region of China. A three-wavelength photoacoustic soot spectrometer (PASS-3) and an aerosol mass spectrometer (AMS) were used to explore the relationship between the ambient measured AAE and the ratio of organic aerosol to BC aerosol, in order to extract the more realistic AAE by pure BC aerosol, which were found to be 0.86, 0.82 and 1.02 at 405nm and 0.70, 0.71, and 0.86 at 532nm in the campaigns of urban-winter, urban-fall, and rural-fall, respectively. Roadway tunnel experiment results further supported the effectiveness of the obtained AAE for pure BC aerosol. In addition, biomass burning experiments proved higher spectral dependence of more-BrC environment and further verified the reliability of the instruments' response. Then, the average light absorption contribution of BrC aerosol was calculated to be 11.7, 6.3 and 12.1% (with total relative uncertainty of 7.5, 6.9 and 10.0%) at 405nm and 10.0, 4.1 and 5.5% (with total relative uncertainty of 6.5, 8.6 and 15.4%) at 532nm of the three campaigns, respectively. These results indicate that the

  3. The single scattering properties of the aerosol particles as aggregated spheres

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Gu, X.; Cheng, T.; Xie, D.; Yu, T.; Chen, H.; Guo, J.

    2012-08-01

    The light scattering and absorption properties of anthropogenic aerosol particles such as soot aggregates are complicated in the temporal and spatial distribution, which introduce uncertainty of radiative forcing on global climate change. In order to study the single scattering properties of anthorpogenic aerosol particles, the structures of these aerosols such as soot paticles and soot-containing mixtures with the sulfate or organic matter, are simulated using the parallel diffusion limited aggregation algorithm (DLA) based on the transmission electron microscope images (TEM). Then, the single scattering properties of randomly oriented aerosols, such as scattering matrix, single scattering albedo (SSA), and asymmetry parameter (AP), are computed using the superposition T-matrix method. The comparisons of the single scattering properties of these specific types of clusters with different morphological and chemical factors such as fractal parameters, aspect ratio, monomer radius, mixture mode and refractive index, indicate that these different impact factors can respectively generate the significant influences on the single scattering properties of these aerosols. The results show that aspect ratio of circumscribed shape has relatively small effect on single scattering properties, for both differences of SSA and AP are less than 0.1. However, mixture modes of soot clusters with larger sulfate particles have remarkably important effects on the scattering and absorption properties of aggregated spheres, and SSA of those soot-containing mixtures are increased in proportion to the ratio of larger weakly absorbing attachments. Therefore, these complex aerosols come from man made pollution cannot be neglected in the aerosol retrievals. The study of the single scattering properties on these kinds of aggregated spheres is important and helpful in remote sensing observations and atmospheric radiation balance computations.

  4. Spatial variation of aerosol optical properties in North China Plain

    NASA Astrophysics Data System (ADS)

    Fan, Xuehua

    2013-04-01

    The column-integrated optical properties of aerosol in Beijing and Xianghe situated at North China Plain were investigated based on Sun/sky radiometer measurements made at Aerosol Robotic Network (AERONET) sites. Only version 2 and level 2 quality-assured data were presented and analyzed in this paper. Time intervals differ for the two sites, with Beijing having 9 years of data (Mar.-May, 2001; Apr., 2002-Dec., 2011),while Xianghe having 6 years of data (Mar.-Apr., 2001;Sep., 2004-Dec.,2011). Monthly mean 500 nm AOT values reach a maximum in June (0.95) and exceed 0.55 from March through September, and the minimum values occur during the late fall and winter months of November through February at Beijing. The monthly mean AOT values at Xianghe are very close to those measured at Beijing. The absolute differences of AOT between the two sites are less than 0.1 except in June and July. The reason of large difference in June and July is the frequently cloud contamination in summer result in the monthly means over the two sites computed from a large number of measurements of different date. The monthly averaged AOT with the same date in June and July are re-computed and the absolute difference of AOT between Beijing and Xianghe reduced to 0.01 and 0.03 in June and July respectively. The monthly mean Angstrom Exponent (AE) in Beijing and Xianghe sites are very close, with the absolute difference less than 0.075. The monthly mean AE in the two sites varied between ~1.0 and ~1.3 except in spring (March-May), therefore clearly dominated by fine mode aerosol for most of the year. All monthly averaged SSA at Beijing showed much lower value as compared to Xianghe though the seasonal variations are similar for the two sites, which indicates that aerosol absorption is greater in Beijing. All monthly averaged imaginary part of refractive index at Beijing has much higher value than Xianghe. The absolute differences of SSA between the two sites range from 0.016 to 0.037 except that

  5. [Development of a photoacoustic spectroscopy system for the measurement of absorption coefficient of atmospheric aerosols].

    PubMed

    Liu, Qiang; Niu, Ming-Sheng; Wang, Gui-Shi; Cao, Zhen-Song; Liu, Kun; Chen, Wei-Dong; Gao, Xiao-Ming

    2013-07-01

    In the present paper, the authors focus on the effect of the resonance frequency shift due to the changes in temperature and humidity on the PA signal, present several methods to control the noise derived form gas flow and vibration from the sampling pump. Based on the efforts mentioned above, a detection limit of 1.4 x 10(-8) W x cm(-1) x Hz(-1/2) was achieved for the measurement of atmospheric aerosols absorption coefficient. During the experiments, the PA cell was calibrated with the absorption of standard NO2 gas at 532 nm and the atmospheric aerosols were measured continuously. The measurement results show that the PAS is suitable for the real-time measurement of the absorption coefficient of atmospheric aerosols in their natural suspended state. PMID:24059163

  6. Light Absorption of Stratospheric Aerosols: Long-Term Trend and Contribution by Aircraft

    NASA Technical Reports Server (NTRS)

    Pueschel , R. F.; Gore, Waren J. Y. (Technical Monitor)

    1997-01-01

    Measurements of aerosol light-absorption coefficients are useful for studies of radiative transfer and heating rates. Ogren appears to have published the first light- absorption coefficients in the stratosphere in 1981, followed by Clarke in 1983 and Pueschel in 1992. Because most stratospheric soot appears to be due to aircraft operations, application of an aircraft soot aerosol emission index to projected fuel consumption suggests a threefold increase of soot loading and light absorption by 2025. Together, those four data sets indicate an increase in mid-visible light extinction at a rate of 6 % per year. This trend is similar to the increase per year of sulfuric acid aerosol and of commercial fleet size. The proportionality between stepped-up aircraft operations above the tropopause and increases in stratospheric soot and sulfuric acid aerosol implicate aircraft as a source of stratospheric pollution. Because the strongly light-absorbing soot and the predominantly light-scattering sulfuric acid aerosol increase at similar rates, however, the mid-visible stratospheric aerosol single scatter albedo is expected to remain constant and not approach a critical value of 0.98 at which stratospheric cooling could change to warming.

  7. Light absorption of brown carbon aerosol in the PRD region of China

    NASA Astrophysics Data System (ADS)

    Yuan, J.-F.; Huang, X.-F.; Cao, L.-M.; Cui, J.; Zhu, Q.; Huang, C.-N.; Lan, Z.-J.; He, L.-Y.

    2015-10-01

    The strong spectral dependence of light absorption of brown carbon (BrC) aerosol is regarded to influence aerosol's radiative forcing significantly. The Absorption Angstrom Exponent (AAE) method was widely used in previous studies to attribute light absorption of BrC at shorter wavelengths for ambient aerosol, with a theoretical assumption that the AAE of "pure" black carbon (BC) aerosol equals to 1.0. In this study, the previous AAE method was improved by statistical analysis and applied in both urban and rural environments in the Pearl River Delta (PRD) region of China. A three-wavelength photo-acoustic soot spectrometer (PASS-3) and aerosol mass spectrometers (AMS) were used to explore the relationship between the measured AAE and the relative abundance of organic aerosol to BC. The regression and extrapolation analysis revealed that the more realistic AAE values for "pure" BC aerosol were 0.86, 0.82, and 1.02 at 405 nm, and 0.70, 0.71, and 0.86 at 532 nm, in the campaigns of urban_winter, urban_fall, and rural_fall, respectively. Roadway tunnel experiments were also conducted, and the results further supported the representativeness of the obtained AAE values for "pure" BC aerosol in the urban environments. Finally, the average aerosol light absorption contribution of BrC was quantified to be 11.7, 6.3, and 12.1 % (with relative uncertainties of 4, 4, and 7 %) at 405 nm, and 10.0, 4.1, and 5.5 % (with relative uncertainties of 2, 2, and 5 %) at 532 nm, in the campaigns of urban_winter, urban_fall, and rural_fall, respectively. The relatively higher BrC absorption contribution at 405 nm in the rural_fall campaign was likely a result of the biomass burning events nearby, which was supported by the biomass burning simulation experiments performed in this study. The results of this paper indicate that the brown carbon contribution to aerosol light absorption at shorter wavelengths is not negligible in the highly urbanized and industrialized PRD region.

  8. A new approach for retrieving the UV-vis optical properties of ambient aerosols

    NASA Astrophysics Data System (ADS)

    Bluvshtein, Nir; Flores, J. Michel; Segev, Lior; Rudich, Yinon

    2016-08-01

    Atmospheric aerosols play an important part in the Earth's energy budget by scattering and absorbing incoming solar and outgoing terrestrial radiation. To quantify the effective radiative forcing due to aerosol-radiation interactions, researchers must obtain a detailed understanding of the spectrally dependent intensive and extensive optical properties of different aerosol types. Our new approach retrieves the optical coefficients and the single-scattering albedo of the total aerosol population over 300 to 650 nm wavelength, using extinction measurements from a broadband cavity-enhanced spectrometer at 315 to 345 nm and 390 to 420 nm, extinction and absorption measurements at 404 nm from a photoacoustic cell coupled to a cavity ring-down spectrometer, and scattering measurements from a three-wavelength integrating nephelometer. By combining these measurements with aerosol size distribution data, we retrieved the time- and wavelength-dependent effective complex refractive index of the aerosols. Retrieval simulations and laboratory measurements of brown carbon proxies showed low absolute errors and good agreement with expected and reported values. Finally, we implemented this new broadband method to achieve continuous spectral- and time-dependent monitoring of ambient aerosol population, including, for the first time, extinction measurements using cavity-enhanced spectrometry in the 315 to 345 nm UV range, in which significant light absorption may occur.

  9. Aerosol Absorption by Black Carbon and Dust: Implications of Climate Change and Air Quality in Asia

    NASA Technical Reports Server (NTRS)

    Chin, Mian

    2010-01-01

    Atmospheric aerosol distributions from 2000 to 2007 are simulated with the global model GOCART to attribute light absorption by aerosol to its composition and sources. We show the seasonal and interannual variations of absorbing aerosols in the atmosphere over Asia, mainly black carbon and dust. and their linkage to the changes of anthropogenic and dust emissions in the region. We compare our results with observations from satellite and ground-based networks, and estimate the importance of black carbon and dust on regional climate forcing and air quality.

  10. Cloud droplet nucleation and its connection to aerosol properties

    SciTech Connect

    Schwartz, S.E.

    1996-04-01

    Anthropogenic aerosols influence the earth`s radiation balance and climate directly, by scattering shortwave (solar) radiation in cloud-free conditions and indirectly, by increasing concentrations of cloud droplets thereby enhancing cloud shortwave reflectivity. These effects are thought to be significant in the context of changes in the earth radiation budget over the industrial period, exerting a radiative forcing that is of comparable magnitude to that of increased concentrations of greenhouse gases over this period but opposite in sign. However the magnitudes of both the direct and indirect aerosol effects are quite uncertain. Much of the uncertainty of the indirect effect arises from incomplete ability to describe changes in cloud properties arising from anthropogenic aerosols. This paper examines recent studies pertaining to the influence of anthropogenic aerosols on loading and properties of aerosols affecting their cloud nucleating properties and indicative of substantial anthropogenic influence on aerosol and cloud properties over the North Atlantic.

  11. Satellite and in-situ derived aerosol optical properties over the TCAP campaign region

    NASA Astrophysics Data System (ADS)

    Chand, D.; Berg, L. K.; Ferrare, R. A.; Barnard, J.; Berkowitz, C. M.; Chapman, E.; Comstock, J. M.; Fast, J. D.; Flynn, C. J.; Hair, J. W.; Hostetler, C. A.; Hubbe, J.; Kassianov, E.; Kluzek, C. D.; Pekour, M. S.; Sedlacek, A. J.; Schmid, B.; Shilling, J. E.; Shinozuka, Y.; Tomlinson, J. M.; Wilson, J. M.; Zelenyuk, A.

    2012-12-01

    The direct radiative effect of natural and anthropogenic aerosol is one of the largest uncertainties in the prediction of climate change at regional and global scales. The uncertainties in atmospheric radiative forcing are in part a result of limited knowledge of aerosol optical properties. In this presentation we discuss in-situ and satellite derived aerosol optical properties obtained within the Two-Column Aerosol Project (TCAP) campaign region, and explore their links with aerosol chemical and physical properties. The TCAP field campaign is designed to provide observations of the size distribution, chemical properties, and optical properties of aerosol within and between two atmospheric columns along the eastern seaboard of the United States. These columns are separated by 200-300 km and were sampled in July 2012 during a summer intensive operation period (IOP) using the U.S. Department of Energy's Gulfstream-1 (G-1) and NASA's B200 aircraft and the surface-based DOE Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) located at Cape Cod. In contrast to the aircraft IOP, the AMF will be operated continuously until the summer of 2013.The surface observations will test the veracity of cloud and radiative transfer models over a wider range of conditions than can be observed via the short-term aircraft IOPs. In this presentation we will examine the spectral dependence of the aerosol optical properties with a focus on in-situ as well as remote sensing observations during the summer (July) over the TCAP region. We will also use multiple years of observations from MODIS, CALIPSO, and OMI satellite sensors and develop the climatology of aerosol optical depth (AOD), single scattering albedo (SSA) and aerosol layer altitudes to put the TCAP observations into a larger perspective. In addition, in-situ observations of light scattering and absorption coefficients made using the G-1, and AOD and aerosol features derived from the NASA High Spectral Resolution Lidar

  12. Model analysis of influences of aerosol mixing state upon its optical properties in East Asia

    NASA Astrophysics Data System (ADS)

    Han, Xiao; Zhang, Meigen; Zhu, Lingyun; Xu, Liren

    2013-07-01

    The air quality model system RAMS (Regional Atmospheric Modeling System)-CMAQ (Models-3 Community Multi-scale Air Quality) coupled with an aerosol optical/radiative module was applied to investigate the impact of different aerosol mixing states (i.e., externally mixed, half externally and half internally mixed, and internally mixed) on radiative forcing in East Asia. The simulation results show that the aerosol optical depth (AOD) generally increased when the aerosol mixing state changed from externally mixed to internally mixed, while the single scattering albedo (SSA) decreased. Therefore, the scattering and absorption properties of aerosols can be significantly affected by the change of aerosol mixing states. Comparison of simulated and observed SSAs at five AERONET (Aerosol Robotic Network) sites suggests that SSA could be better estimated by considering aerosol particles to be internally mixed. Model analysis indicates that the impact of aerosol mixing state upon aerosol direct radiative forcing (DRF) is complex. Generally, the cooling effect of aerosols over East Asia are enhanced in the northern part of East Asia (Northern China, Korean peninsula, and the surrounding area of Japan) and are reduced in the southern part of East Asia (Sichuan Basin and Southeast China) by internal mixing process, and the variation range can reach ±5 W m-2. The analysis shows that the internal mixing between inorganic salt and dust is likely the main reason that the cooling effect strengthens. Conversely, the internal mixture of anthropogenic aerosols, including sulfate, nitrate, ammonium, black carbon, and organic carbon, could obviously weaken the cooling effect.

  13. AERONET-based microphysical and optical properties of smoke-dominated aerosol near source regions and transported over oceans, and implications for satellite retrievals of aerosol optical depth

    NASA Astrophysics Data System (ADS)

    Sayer, A. M.; Hsu, N. C.; Eck, T. F.; Smirnov, A.; Holben, B. N.

    2013-09-01

    Smoke aerosols from biomass burning are an important component of the global aerosol cycle. Analysis of Aerosol Robotic Network (AERONET) retrievals of size distribution and refractive index reveals variety between biomass burning aerosols in different global source regions, in terms of aerosol particle size and single scatter albedo (SSA). Case studies of smoke transported to coastal/island AERONET sites also mostly lie within the range of variability at near-source sites. Two broad ''families'' of aerosol properties are found, corresponding to sites dominated by boreal forest burning (larger, broader fine mode, with midvisible SSA ∼0.95), and those influenced by grass, shrub, or crop burning with additional forest contributions (smaller, narrower particles with SSA ∼0.88-0.9 in the midvisible). The strongest absorption is seen in southern African savannah at Mongu (Zambia), with average SSA ∼0.85 in the midvisible. These can serve as candidate sets of aerosol microphysical/optical properties for use in satellite aerosol optical depth (AOD) retrieval algorithms. The models presently adopted by these algorithms over ocean are often insufficiently absorbing to represent these biomass burning aerosols. A corollary of this is an underestimate of AOD in smoke outflow regions, which has important consequences for applications of these satellite datasets.

  14. Aeronet-based Microphysical and Optical Properties of Smoke-dominated Aerosol near Source Regions and Transported over Oceans, and Implications for Satellite Retrievals of Aerosol Optical Depth

    NASA Technical Reports Server (NTRS)

    Sayer, A. M.; Hsu, N. C.; Eck, T. F.; Smirnov, A.; Holben, B. N.

    2013-01-01

    Smoke aerosols from biomass burning are an important component of the global aerosol cycle. Analysis of Aerosol Robotic Network (AERONET) retrievals of size distribution and refractive index reveals variety between biomass burning aerosols in different global source regions, in terms of aerosol particle size and single scatter albedo (SSA). Case studies of smoke transported to coastal/island AERONET sites also mostly lie within the range of variability at near-source sites. Two broad families of aerosol properties are found, corresponding to sites dominated by boreal forest burning (larger, broader fine mode, with midvisible SSA 0.95), and those influenced by grass, shrub, or crop burning with additional forest contributions (smaller, narrower particles with SSA 0.88-0.9 in the midvisible). The strongest absorption is seen in southern African savanna at Mongu (Zambia), with average SSA 0.85 in the midvisible. These can serve as candidate sets of aerosol microphysicaloptical properties for use in satellite aerosol optical depth (AOD) retrieval algorithms. The models presently adopted by these algorithms over ocean are often insufficiently absorbing to represent these biomass burning aerosols. A corollary of this is an underestimate of AOD in smoke outflow regions, which has important consequences for applications of these satellite datasets.

  15. A photophonic instrument concept to measure atmospheric aerosol absorption. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Engle, C. D.

    1982-01-01

    A laboratory model of an instrument to measure the absorption of atmospheric aerosols was designed, built, and tested. The design was based on the photophonic phenomenon discovered by Bell and an acoustic resonator developed by Helmholtz. Experiments were done to show ways the signal amplitude could be improved and the noise reduced and to confirm the instrument was sensitive enough to be practical. The research was undertaken to develop concepts which show promise of being improvements on the instruments that are presently used to measure the absorption of the Sun's radiation by the Earth's atmospheric aerosols.

  16. Elevated aerosol layers modify the O2-O2 absorption measured by ground-based MAX-DOAS

    NASA Astrophysics Data System (ADS)

    Ortega, Ivan; Berg, Larry K.; Ferrare, Richard A.; Hair, Johnathan W.; Hostetler, Chris A.; Volkamer, Rainer

    2016-06-01

    The oxygen collisional complex (O2-O2, or O4) is a greenhouse gas, and a calibration trace gas used to infer aerosol and cloud properties by Differential Optical Absorption Spectroscopy (DOAS). Recent reports suggest the need for an O4 correction factor (CFO4) when comparing simulated and measured O4 differential slant column densities (dSCD) by passive DOAS. We investigate the sensitivity of O4 dSCD simulations at ultraviolet (360 nm) and visible (477 nm) wavelengths towards separately measured aerosol extinction profiles. Measurements were conducted by the University of Colorado 2D-MAX-DOAS instrument and NASA's multispectral High Spectral Resolution Lidar (HSRL-2) during the Two Column Aerosol Project (TCAP) at Cape Cod, MA in July 2012. During two case study days with (1) high aerosol load (17 July, AOD~0.35 at 477 nm), and (2) near molecular scattering conditions (22 July, AOD<0.10 at 477 nm) the measured and calculated O4 dSCDs agreed within 6.4±0.4% (360 nm) and 4.7±0.6% (477 nm) if the HSRL-2 profiles were used as input to the calculations. However, if in the calculations the aerosol is confined to the surface layer (while keeping AOD constant) we find 0.53aerosol layers, unless accounted for, can cause negative bias in the simulated O4 dSCDs that can explain CFO4. The air density and aerosol profile aloft needs to be taken into account when interpreting the O4 from ground-based MAX-DOAS. Opportunities to identify and better characterize these elevated layers are also discussed.

  17. Aerosol and CCN properties at Princess Elisabeth station, East Antarctica: seasonality, new particle formation events and properties around precipitation events

    NASA Astrophysics Data System (ADS)

    Mangold, Alexander; Laffineur, Quentin; De Backer, Hugo; Herenz, Paul; Wex, Heike; Gossart, Alexandra; Souverijns, Niels; Gorodetskaya, Irina; Van Lipzig, Nicole

    2016-04-01

    Since 2010, several complementary ground-based instruments for measuring the aerosol composition of the Antarctic atmosphere have been operated at the Belgian Antarctic research station Princess Elisabeth, in Dronning Maud Land, East Antarctica (71.95° S, 23.35° E, 1390 m asl.). In addition, three ground-based remote sensing instruments for cloud and precipitation observations have been installed for continuous operation, including a ceilometer (cloud base height, type, vertical extent), a 24 Ghz micro-rain radar (vertical profiles of radar effective reflectivity and Doppler velocity), and a pyrometer (cloud base temperature). The station is inhabited from November to end of February and operates under remote control during the other months. In this contribution, the general aerosol and cloud condensation nuclei (CCN) properties will be described with a special focus on new particle formation events and around precipitation events. New particle formation events are important for the atmospheric aerosol budget and they also show that aerosols are not only transported to Antarctica but are also produced there, also inland. Aerosols are essential for cloud formation and therefore also for precipitation, which is the only source for mass gain of the Antarctic ice sheet. Measured aerosol properties comprise size distribution, total number, total mass concentration, mass concentration of light-absorbing aerosol and absorption coefficient and total scattering coefficient. In addition, a CCN counter has been operated during austral summers 2013/14, 2014/15 and 2015/16. The baseline total number concentration N-total was around some hundreds of particles/cm3. During new particle formation events N-total increased to some thousands of particles/cm3. Simultaneous measurements of N-total, size distribution and CCN number revealed that mostly the number of particles smaller than 100 nm increased and that the concentration of cloud condensation nuclei increased only very

  18. Optical properties of aerosol emissions from biomass burning in the tropics, BASE-A

    NASA Technical Reports Server (NTRS)

    Holben, Brent N.; Kaufman, Yoram J.; Setzer, Alberto W.; Tanre, Didre D.; Ward, Darold E.

    1991-01-01

    Ground-based and airborne measurements of biomass-burning smoke particle optical properties, obtained with a view to aerosol-absorption properties, are presented as a function of time and atmospheric height. The wavelength dependence of the optical thickness can be explained by a log-normal size distribution, with particles' effective radius varying between 0.1 and 0.2 microns. The strong correlation noted between aerosol particle profile and CO profile indicates that smoke particulates constitute a good tracer for emission trace gases from tropical biomass burning.

  19. Long term measurements of aerosol optical properties at a primary forest site in Amazonia

    NASA Astrophysics Data System (ADS)

    Rizzo, L. V.; Artaxo, P.; Müller, T.; Wiedensohler, A.; Paixão, M.; Cirino, G. G.; Arana, A.; Swietlicki, E.; Roldin, P.; Fors, E. O.; Wiedemann, K. T.; Leal, L. S. M.; Kulmala, M.

    2013-03-01

    A long term experiment was conducted in a primary forest area in Amazonia, with continuous in-situ measurements of aerosol optical properties between February 2008 and April 2011, comprising, to our knowledge, the longest database ever in the Amazon Basin. Two major classes of aerosol particles, with significantly different optical properties were identified: coarse mode predominant biogenic aerosols in the wet season (January-June), naturally released by the forest metabolism, and fine mode dominated biomass burning aerosols in the dry season (July-December), transported from regional fires. Dry particle median scattering coefficients at the wavelength of 550 nm increased from 6.3 Mm-1 to 22 Mm-1, whereas absorption at 637 nm increased from 0.5 Mm-1 to 2.8 Mm-1 from wet to dry season. Most of the scattering in the dry season was attributed to the predominance of fine mode (PM2) particles (40-80% of PM10 mass), while the enhanced absorption coefficients are attributed to the presence of light absorbing aerosols from biomass burning. As both scattering and absorption increased in the dry season, the single scattering albedo (SSA) did not show a significant seasonal variability, in average 0.86 ± 0.08 at 637 nm for dry aerosols. Measured particle optical properties were used to estimate the aerosol forcing efficiency at the top of the atmosphere. Results indicate that in this primary forest site the radiative balance was dominated by the cloud cover, particularly in the wet season. Due to the high cloud fractions, the aerosol forcing efficiency absolute values were below -3.5 W m-2 in 70% of the wet season days and in 46% of the dry season days. Besides the seasonal variation, the influence of out-of-Basin aerosol sources was observed occasionally. Periods of influence of the Manaus urban plume were detected, characterized by a consistent increase on particle scattering (factor 2.5) and absorption coefficients (factor 5). Episodes of biomass burning and mineral dust

  20. Long term measurements of aerosol optical properties at a pristine forest site in Amazonia

    NASA Astrophysics Data System (ADS)

    Rizzo, L. V.; Artaxo, P.; Müller, T.; Wiedensohler, A.; Paixão, M.; Cirino, G. G.; Arana, A.; Swietlicki, E.; Roldin, P.; Fors, E. O.; Wiedemann, K. T.; Leal, L. S. M.; Kulmala, M.

    2012-09-01

    A long term experiment was conducted in a pristine area in the Amazon forest, with continuous in situ measurements of aerosol optical properties between February 2008 and April 2011, comprising, to our knowledge, the longest database ever in Amazonia. Two types of aerosol particles, with significantly different optical properties were identified: coarse mode predominant biogenic aerosols in the wet season (January-June), naturally released by the forest metabolism, and fine mode dominated biomass burning aerosols in the dry season (July-December), transported from regional fires. Dry particle median scattering coefficients at the wavelength of 550 nm increased from 6.3 Mm-1 to 22 Mm-1, whereas absorption at 637 nm increased from 0.5 Mm-1 to 2.8 Mm-1 from wet to dry season. Most of the scattering in the dry season was attributed to the predominance of fine mode particles (40-80% of PM10 mass), while the enhanced absorption coefficients are attributed to the presence of light absorbing aerosols from biomass burning. As both scattering and absorption increased in the dry season, the single scattering albedo (SSA) did not show a significant seasonal variability, in average 0.86 ± 0.08 at 637 nm for dry particles. Measured particle optical properties were used to estimate the aerosol forcing efficiency at the top of the atmosphere. Results indicate that in this pristine forest site the radiative balance was dominated by the cloud cover, or, in other words, the aerosol indirect effect predominated over the direct effect, particularly in the wet season. Due to the high cloud fractions, the aerosol forcing efficiency was below -3.5 W m-2 in 70% of the wet season days and in 46% of the dry season days. These values are lower than the ones reported in the literature, which are based on remote sensing data. Besides the seasonal variation, the influence of external aerosol sources was observed occasionally. Periods of influence of the Manaus urban plume were detected

  1. Characterization of aerosol properties from polarimetric satellite observations using GRASP algorithm

    NASA Astrophysics Data System (ADS)

    Dubovik, Oleg; Litvinov, Pavel; Lapyonok, Tatyana; Ducos, Fabrice; Huang, Xin; Lopatin, Anton; Fuertes, David; Derimian, Yevgeny

    2016-04-01

    GRASP (Generalized Retrieval of Aerosol and Surface Properties) is recently developed (Dubovik et al. 2011, 2014) sophisticated algorithm of new generation. The algorithm retrieves aerosol and surface properties simultaneously. It realizes statistically optimized fitting using multi-pixel concept when the retrieval is implemented simultaneously for a large group of satellite pixels. This allows for using additional a priori information about limited variability of aerosol of surface properties in time and/or space. GPASP searches in continuous space of solutions and doesn't utilize look-up-tables. GRASP doesn't use any location specific information about aerosol or surface type in the each observed pixel, and the results are essentially driven by observations. However GRASP retrieval takes longer computational time compare to most conventional algorithms. This main practical challenge of employing GRASP has been addressed during last two years and GRASP algorithm has been significantly optimized and adapted to operational needs. As a result of this optimization and GRASP has been accelerated to the level acceptable for processing large volumes of satellite observations. Recently GRASP has been applied to multi-years archives of PARASO/POLDER. The analysis of the results shows that GRASP retrievals provide rather robust and comprehensive aerosol characterization including such properties as absorption and aerosol type even for observations over bright surfaces and for monitoring very high aerosol loading events (with AOD up to 3 or 4). In addition, the attempts to estimate such aerosol characteristics as aerosol height, air quality, radiative forcing, etc. have been made. The results and illustrations will be presented.

  2. Direct radiative forcing and atmospheric absorption by boundary layer aerosols in the southeastern US: model estimates on the basis of new observations

    NASA Astrophysics Data System (ADS)

    Yu, Shaocai; Zender, Charles S.; Saxena, V. K.

    In an effort to reduce uncertainties in the quantification of aerosol direct radiative forcing (ADRF) in the southeastern United States (US), a field column experiment was conducted to measure aerosol radiative properties and effects at Mt. Mitchell, North Carolina, and at an adjacent valley site. The experimental period was from June 1995 to mid-December 1995. The aerosol optical properties (single scattering albedo and asymmetry factor) needed to compute ADRF were obtained on the basis of a procedure involving a Mie code and a radiative transfer code in conjunction with the retrieved aerosol size distribution, aerosol optical depth, and diffuse-to-direct solar irradiance ratio. The regional values of ADRF at the surface and top of atmosphere (TOA), and atmospheric aerosol absorption are derived using the obtained aerosol optical properties as inputs to the column radiation model (CRM) of the community climate model (CCM3). The cloud-free instantaneous TOA ADRFs for highly polluted (HP), marine (M) and continental (C) air masses range from 20.3 to -24.8, 1.3 to -10.4, and 1.9 to -13.4 W m -2, respectively. The mean cloud-free 24-h ADRFs at the TOA (at the surface) for HP, M, and C air masses are estimated to be -8±4 (-33±16), -7±4 (-13±8), and -0.14±0.05 (-8±3) W m -2, respectively. On the assumption that the fractional coverage of clouds is 0.61, the annual mean ADRFs at the TOA and the surface are -2±1, and -7±2 W m -2, respectively. This also implies that aerosols currently heat the atmosphere over the southeastern US by 5±3 W m -2 on annual timescales due to the aerosol absorption in the troposphere.

  3. Climatology of Aerosol Optical Properties in Southern Africa

    NASA Technical Reports Server (NTRS)

    Queface, Antonio J.; Piketh, Stuart J.; Eck, Thomas F.; Tsay, Si-Chee

    2011-01-01

    A thorough regionally dependent understanding of optical properties of aerosols and their spatial and temporal distribution is required before we can accurately evaluate aerosol effects in the climate system. Long term measurements of aerosol optical depth, Angstrom exponent and retrieved single scattering albedo and size distribution, were analyzed and compiled into an aerosol optical properties climatology for southern Africa. Monitoring of aerosol parameters have been made by the AERONET program since the middle of the last decade in southern Africa. This valuable information provided an opportunity for understanding how aerosols of different types influence the regional radiation budget. Two long term sites, Mongu in Zambia and Skukuza in South Africa formed the core sources of data in this study. Results show that seasonal variation of aerosol optical thicknesses at 500 nm in southern Africa are characterized by low seasonal multi-month mean values (0.11 to 0.17) from December to May, medium values (0.20 to 0.27) between June and August, and high to very high values (0.30 to 0.46) during September to November. The spatial distribution of aerosol loadings shows that the north has high magnitudes than the south in the biomass burning season and the opposite in none biomass burning season. From the present aerosol data, no long term discernable trends are observable in aerosol concentrations in this region. This study also reveals that biomass burning aerosols contribute the bulk of the aerosol loading in August-October. Therefore if biomass burning could be controlled, southern Africa will experience a significant reduction in total atmospheric aerosol loading. In addition to that, aerosol volume size distribution is characterized by low concentrations in the non biomass burning period and well balanced particle size contributions of both coarse and fine modes. In contrast high concentrations are characteristic of biomass burning period, combined with

  4. Imaginary refractive index and other microphysical properties of volcanic ash, Sarahan dust, and other mineral aerosols

    NASA Astrophysics Data System (ADS)

    Rocha Lima, A.; Martins, J.; Krotkov, N. A.; Artaxo, P.; Todd, M.; Ben Ami, Y.; Dolgos, G.; Espinosa, R.

    2013-12-01

    Aerosol properties are essential to support remote sensing measurements, atmospheric circulation and climate models. This research aims to improve the understanding of the optical and microphysical properties of different types of aerosols particles. Samples of volcanic ash, Saharan dust and other mineral aerosols particles were analyzed by different techniques. Ground samples were sieved down to 45um, de-agglomerated and resuspended in the laboratory using a Fluidized Bed Aerosol Generator (FBAG). Particles were collected on Nuclepore filters into PM10, PM2.5, or PM1.0. and analyzed by different techniques, such as Scanning Electron Microscopy (SEM) for determination of size distribution and shape, spectral reflectance for determination of the optical absorption properties as a function of the wavelength, material density, and X-Ray fluorescence for the elemental composition. The spectral imaginary part of refractive index from the UV to the short wave infrared (SWIR) wavelength was derived empirically from the measurements of the spectral mass absorption coefficient, size distribution and density of the material. Some selected samples were also analyzed with the Polarized Imaging Nephelometer (PI-Neph) instrument for the characterization of the aerosol polarized phase function. This work compares results of the spectral refractive index of different materials obtained by our methodology with those available in the literature. In some cases there are significant differences both in magnitude and spectral dependence of the imaginary refractive index. These differences are evaluated and discussed in this work.

  5. Studying Taklamakan aerosol properties with lidar (STAPL)

    NASA Astrophysics Data System (ADS)

    Cottle, Paul; Mueller, Detlef; Shin, Dong-Ho; Zhang, Xiao Xiao; Feng, Guanglong; McKendry, Ian; Strawbridge, Kevin

    2013-10-01

    By now, the global impacts of atmospheric dust have been well-established. Nevertheless, relevant properties such as size distribution, depolarization ratio, and even single-scattering albedo have been shown to vary substantially between dust producing regions and are also strongly dependant on the conditions under which the dust is emitted. Even greater variations have been documented during the process of long-range transport. With continued improvement of detection technologies, research focus is increasingly turning to refinement of our knowledge of these properties of dust in order to better account for the presence of dust in models and data analysis. The purpose of this study is to use a combination of lidar data and models to directly observe the changing properties of dust layers as they are transported from their origin in the Taklamakan Desert of western China. With the co-operation of the Xinjiang Institute of Ecology and Geography, a portable micropulse lidar system was installed at Aksu National Field on the northern edge of the Tarim Basin in late April 2013, during the Spring dust storm season. Over six days, data were collected on the optical properties of dust emissions passing over this location. The measurements of this lidar have shown the dust over Aksu on these days to have a significantly higher depolarization ratio than has been previously reported for the region. Model results show this dust was then transported across the region at least as far as Korea and Japan. Models from the Naval Aerosol Analysis and Prediction System (NAAPS) show that during transport the dust layers became intermixed with sulfate emissions from industrial sources in China as well as smoke from wildfires burning in south-east Asia and Siberia. The multi-wavelength raman-elastic lidar located in Gwangju South Korea was used to observe the vertical structure of the layers as well as optical properties such as colour ratio, depolarization ratio and extinction

  6. Evaluating Global Aerosol Models and Aerosol and Water Vapor Properties Near Clouds

    SciTech Connect

    Richard A. Ferrare; David D. Turner

    2011-09-01

    Project goals: (1) Use the routine surface and airborne measurements at the ARM SGP site, and the routine surface measurements at the NSA site, to continue our evaluations of model aerosol simulations; (2) Determine the degree to which the Raman lidar measurements of water vapor and aerosol scattering and extinction can be used to remotely characterize the aerosol humidification factor; (3) Use the high temporal resolution CARL data to examine how aerosol properties vary near clouds; and (4) Use the high temporal resolution CARL and Atmospheric Emitted Radiance Interferometer (AERI) data to quantify entrainment in optically thin continental cumulus clouds.

  7. Light absorption of brown carbon aerosol in the PRD region of China

    NASA Astrophysics Data System (ADS)

    Yuan, J.-F.; Huang, X.-F.; Cao, L.-M.; Cui, J.; Zhu, Q.; Huang, C.-N.; Lan, Z.-J.; He, L.-Y.

    2016-02-01

    The strong spectral dependence of light absorption of brown carbon (BrC) aerosol is regarded to influence aerosol's radiative forcing significantly. The Absorption Angstrom Exponent (AAE) method has been widely used in previous studies to attribute light absorption of BrC at shorter wavelengths for ambient aerosols, with a theoretical assumption that the AAE of "pure" black carbon (BC) aerosol equals to 1.0. In this study, the AAE method was applied to both urban and rural environments in the Pearl River Delta (PRD) region of China, with an improvement of constraining the realistic AAE of "pure" BC through statistical analysis of on-line measurement data. A three-wavelength photo-acoustic soot spectrometer (PASS-3) and aerosol mass spectrometers (AMS) were used to explore the relationship between the measured AAE and the relative abundance of organic aerosol to BC. The regression and extrapolation analysis revealed that more realistic AAE values for "pure" BC aerosol (AAEBC) were 0.86, 0.82, and 1.02 between 405 and 781 nm, and 0.70, 0.71, and 0.86 between 532 and 781 nm, in the campaigns of urbanwinter, urbanfall, and ruralfall, respectively. Roadway tunnel experiments were conducted and the results further confirmed the representativeness of the obtained AAEBC values for the urban environment. Finally, the average light absorption contributions of BrC (± relative uncertainties) at 405 nm were quantified to be 11.7 % (±5 %), 6.3 % (±4 %), and 12.1 % (±7 %) in the campaigns of urbanwinter, urbanfall, and ruralfall, respectively, and those at 532 nm were 10.0 % (±2 %), 4.1 % (±3 %), and 5.5 % (±5 %), respectively. The relatively higher BrC absorption contribution at 405 nm in the ruralfall campaign could be reasonably attributed to the biomass burning events nearby, which was then directly supported by the biomass burning simulation experiments performed in this study. This paper indicates that the BrC contribution to total aerosol light absorption at shorter

  8. Measurements of Aerosol Vertical Profiles and Optical Properties during INDOEX 1999 Using Micro-Pulse Lidars

    NASA Technical Reports Server (NTRS)

    Welton, Ellsworth J.; Voss, Kenneth J.; Quinn, Patricia K.; Flatau, Piotr J.; Markowicz, Krzysztof; Campbell, James R.; Spinhirne, James D.; Gordon, Howard R.; Johnson, James E.; Starr, David OC. (Technical Monitor)

    2001-01-01

    Micro-pulse lidar systems (MPL) were used to measure aerosol properties during the Indian Ocean Experiment (INDOEX) 1999 field phase. Measurements were made from two platforms: the NOAA ship RN Ronald H. Brown, and the Kaashidhoo Climate Observatory (KCO) in the Maldives. Sunphotometers were used to provide aerosol optical depths (AOD) needed to calibrate the MPL. This study focuses on the height distribution and optical properties (at 523 nm) of aerosols observed during the campaign. The height of the highest aerosols (top height) was calculated and found to be below 4 km for most of the cruise. The marine boundary layer (MBL) top was calculated and found to be less than 1 km. MPL results were combined with air mass trajectories, radiosonde profiles of temperature and humidity, and aerosol concentration and optical measurements. Humidity varied from approximately 80% near the surface to 50% near the top height during the entire cruise. The average value and standard deviation of aerosol optical parameters were determined for characteristic air mass regimes. Marine aerosols in the absence of any continental influence were found to have an AOD of 0.05 +/- 0.03, an extinction-to-backscatter ratio (S-ratio) of 33 +/- 6 sr, and peak extinction values around 0.05/km (near the MBL top). The marine results are shown to be in agreement with previously measured and expected values. Polluted marine areas over the Indian Ocean, influenced by continental aerosols, had AOD values in excess of 0.2, S-ratios well above 40 sr, and peak extinction values approximately 0.20/km (near the MBL top). The polluted marine results are shown to be similar to previously published values for continental aerosols. Comparisons between MPL derived extinction near the ship (75 m) and extinction calculated at ship-level using scattering measured by a nephelometer and absorption using a PSAP were conducted. The comparisons indicated that the MPL algorithm (using a constant S-ratio throughout the

  9. Attribution of aerosol light absorption to black carbon, brown carbon, and dust in China - interpretations of atmospheric measurements during EAST-AIRE

    NASA Astrophysics Data System (ADS)

    Yang, M.; Howell, S. G.; Zhuang, J.; Huebert, B. J.

    2009-03-01

    Black carbon, brown carbon, and mineral dust are three of the most important light absorbing aerosols. Their optical properties differ greatly and are distinctive functions of the wavelength of light. Most optical instruments that quantify light absorption, however, are unable to distinguish one type of absorbing aerosol from another. It is thus instructive to separate total absorption from these different light absorbers to gain a better understanding of the optical characteristics of each aerosol type. During the EAST-AIRE (East Asian Study of Tropospheric Aerosols: an International Regional Experiment) campaign near Beijing, we measured light scattering using a nephelometer, and light absorption using an aethalometer and a particulate soot absorption photometer. We also measured the total mass concentrations of carbonaceous (elemental and organic carbon) and inorganic particulates, as well as aerosol number and mass distributions. We were able to identify periods during the campaign that were dominated by dust, biomass burning, fresh (industrial) chimney plumes, other coal burning pollution, and relatively clean (background) air for Northern China. Each of these air masses possessed distinct intensive optical properties, including the single scatter albedo and Ångstrom exponents. Based on the wavelength-dependence and particle size distribution, we apportioned total light absorption to black carbon, brown carbon, and dust; their mass absorption efficiencies at 550 nm were estimated to be 9.5, 0.5 (a lower limit value), and 0.03 m2/g, respectively. While agreeing with the common consensus that black carbon is the most important light absorber in the mid-visible, we demonstrated that brown carbon and dust could also cause significant absorption, especially at shorter wavelengths.

  10. Attribution of aerosol light absorption to black carbon, brown carbon, and dust in China - interpretations of atmospheric measurements during EAST-AIRE

    NASA Astrophysics Data System (ADS)

    Yang, M.; Howell, S. G.; Zhuang, J.; Huebert, B. J.

    2008-06-01

    Black carbon, brown carbon, and mineral dust are three of the most important light absorbing aerosols. Their optical properties differ greatly and are distinctive functions of the wavelength of light. Most optical instruments that quantify light absorption, however, are unable to distinguish one type of absorbing aerosol from another. It is thus instructive to separate total absorption from these different light absorbers to gain a better understanding of the optical characteristics of each aerosol type. During the EAST-AIRE (East Asian Study of Tropospheric Aerosols: an International Regional Experiment) campaign near Beijing, we measured light scattering using a nephelometer, and light absorption using an aethalometer and a particulate soot absorption photometer. We also measured the total mass concentrations of carbonaceous (elemental and organic carbon) and inorganic particulates, as well as aerosol number and mass distributions. We were able to identify periods during the campaign that were dominated by dust, biomass burning, fresh (industrial) chimney plumes, other coal burning pollution, and relatively clean (background) air for Northern China. Each of these air masses possessed distinct intensive optical properties, including the single scatter albedo and Ångstrom exponents. Based on the wavelength-dependence and particle size distribution, we apportioned total light absorption to black carbon, brown carbon, and dust; their mass absorption efficiencies at 550 nm were estimated to be 9.5, 0.5, and 0.03 m2/g, respectively. While agreeing with the common consensus that BC is the most important light absorber in the mid-visible, we demonstrated that brown carbon and dust could also cause significant absorption, especially at shorter wavelengths.

  11. Reduction in biomass burning aerosol light absorption upon humidification: Roles of inorganically-induced hygroscopicity, particle collapse, and photoacoustic heat and mass transfer

    SciTech Connect

    lewis, Kristen A.; Arnott, W. P.; Moosmuller, H.; Chakrabarti, Raj; Carrico, Christian M.; Kreidenweis, Sonia M.; Day, Derek E.; Malm, William C.; Laskin, Alexander; Jimenez, Jose L.; Ulbrich, Ingrid M.; Huffman, John A.; Onasch, Timothy B.; Trimborn, Achim; Liu, Li; Mishchenko, M.

    2009-11-27

    Smoke particle emissions from the combustion of biomass fuels typical for the western and southeastern United States were studied and compared under high humidity and ambient conditions in the laboratory. The fuels used are Montana ponderosa pine (Pinus ponderosa), southern California chamise (Adenostoma fasciculatum), and Florida saw palmetto (Serenoa repens). Information on the non-refractory chemical composition of biomass burning aerosol from each fuel was obtained with an aerosol mass spectrometer and through estimation of the black carbon concentration from light absorption measurements at 870 nm. Changes in the optical and physical particle properties under high humidity conditions were observed for hygroscopic smoke particles containing substantial inorganic mass fractions that were emitted from combustion of chamise and palmetto fuels. Light scattering cross sections increased under high humidity for these particles, consistent with the hygroscopic growth measured for 100 nm particles in HTDMA measurements. Photoacoustic measurements of aerosol light absorption coefficients reveal a 20% reduction with increasing relative humidity, contrary to the expectation of light absorption enhancement by the liquid coating taken up by hygroscopic particles. This reduction is hypothesized to arise from two mechanisms: 1. Shielding of inner monomers after particle consolidation or collapse with water uptake; 2. The contribution of mass transfer through evaporation and condensation at high relative humidity to the usual heat transfer pathway for energy release by laser heated particles in the photoacoustic measurement of aerosol light absorption. The mass transfer contribution is used to evaluate the fraction of aerosol surface covered with liquid water solution as a function of RH.

  12. Using aerosol light absorption measurements for the quantitative determination of wood burning and traffic emission contributions to particulate matter.

    PubMed

    Sandradewi, Jisca; Prévôt, Andre S H; Szidat, Sönke; Perron, Nolwenn; Alfarra, M Rami; Lanz, Valentin A; Weingartner, Ernest; Baltensperger, Urs

    2008-05-01

    A source apportionment study was performed for particulate matter in the small village of Roveredo, Switzerland, where more than 70% of the households use wood burning for heating purposes. A two-lane trans-Alpine highway passes through the village and contributes to the total aerosol burden in the area. The village is located in a steep Alpine valley characterized by strong and persistent temperature inversions during winter, especially from December to February. During two winter and one early spring campaigns, a seven-wavelength aethalometer, high volume (HIVOL) samplers, an Aerodyne quadrupole aerosol mass spectrometer (AMS), an optical particle counter (OPC), and a Sunset Laboratory OCEC analyzer were deployed to study the contribution of wood burning and traffic aerosols to particulate matter. A linear regression model of the carbonaceous particulate mass in the submicrometer size range CM(PM1) as a function of aerosol light absorption properties measured by the aethalometer is introduced to estimate the particulate mass from wood burning and traffic (PM(wb), PM(traffic)). This model was calibrated with analyses from the 14C method using HIVOL filter measurements. These results indicate that light absorption exponents of 1.1 for traffic and 1.8-1.9 for wood burning calculated from the light absorption at 470 and 950 nanometers should be used to obtain agreement of the two methods regarding the relative wood burning and traffic emission contributions to CM(PM1) and also to black carbon. The resulting PM(wb) and PM(traffic) values explain 86% of the variance of the CM(PM1) and contribute, on average, 88 and 12% to CM(PM1), respectively. The black carbon is estimated to be 51% due to wood burning and 49% due to traffic emissions. The average organic carbon/total carbon (OC/TC) values were estimated to be 0.52 for traffic and 0.88 for wood burning particulate emissions.

  13. Aerosol Properties over the Indo-Gangetic Plain: A Mesoscale Perspective from the TIGERZ Experiment

    NASA Technical Reports Server (NTRS)

    Giles, David M.; Holben, Brent N.; Tripathi, Sachchida; Eck, Thomas F.; Newcomb, W. Wayne; Slutsker, Ilya; Dickerson, Russell R.; Thompson, Anne M.; Mattoo, Shana; Wang, Sheng-Hsiang; Singh, Remesh P.; Sinyuk, Aliaksandr; Schafer, Joel S.

    2011-01-01

    High aerosol loading over the northern Indian subcontinent can result in poor air quality leading to human health consequences and climate perturbations. The international 2008 TIGERZ experiment intensive operational period (IOP) was conducted in the Indo \\Gangetic Plain (IGP) around the industrial city of Kanpur (26.51degN, 80.23deg E), India, during the premonsoon (April-June). Aerosol Robotic Network (AERONET) Sun photometers performed frequent measurements of aerosol properties at temporary sites distributed within an area covering 50 sq km around Kanpur to characterize pollution and dust in a region where complex aerosol mixtures and semi \\bright surface effects complicate satellite retrieval algorithms. TIGERZ IOP Sun photometers quantified aerosol optical depth (AOD) increases up to 0.10 within and downwind of the city, with urban emissions accounting for 10 C20% of the IGP aerosol loading on deployment days. TIGERZ IOP area \\averaged volume size distribution and single scattering albedo retrievals indicated spatially homogeneous, uniformly sized, spectrally absorbing pollution and dust particles. Aerosol absorption and size relationships were used to categorize black carbon and dust as dominant absorbers and to identify a third category in which both black carbon and dust dominate absorption.Moderate Resolution Imaging Spectroradiometer (MODIS) AOD retrievals with the lowest quality assurance (QA > or = 0) flags were biased high with respect to TIGERZ IOP area \\averaged measurements. MODIS AOD retrievals with QA 0 had moderate correlation (R(sup 2) = 0.52-69) with the Kanpur AERONET site, whereas retrievals with QA > 0 were limited in number. Mesoscale \\distributed Sun photometers quantified temporal and spatial variability of aerosol properties, and these results were used to validate satellite retrievals.

  14. Aerosol properties over the Indo-Gangetic Plain: A mesoscale perspective from the TIGERZ experiment

    NASA Astrophysics Data System (ADS)

    Giles, David M.; Holben, Brent N.; Tripathi, Sachchida N.; Eck, Thomas F.; Newcomb, W. Wayne; Slutsker, Ilya; Dickerson, Russell R.; Thompson, Anne M.; Mattoo, Shana; Wang, Sheng-Hsiang; Singh, Remesh P.; Sinyuk, Aliaksandr; Schafer, Joel S.

    2011-09-01

    High aerosol loading over the northern Indian subcontinent can result in poor air quality leading to human health consequences and climate perturbations. The international 2008 TIGERZ experiment intensive operational period (IOP) was conducted in the Indo-Gangetic Plain (IGP) around the industrial city of Kanpur (26.51°N, 80.23°E), India, during the premonsoon (April-June). Aerosol Robotic Network (AERONET) Sun photometers performed frequent measurements of aerosol properties at temporary sites distributed within an area covering ˜50 km2 around Kanpur to characterize pollution and dust in a region where complex aerosol mixtures and semi-bright surface effects complicate satellite retrieval algorithms. TIGERZ IOP Sun photometers quantified aerosol optical depth (AOD) increases up to ˜0.10 within and downwind of the city, with urban emissions accounting for ˜10-20% of the IGP aerosol loading on deployment days. TIGERZ IOP area-averaged volume size distribution and single scattering albedo retrievals indicated spatially homogeneous, uniformly sized, spectrally absorbing pollution and dust particles. Aerosol absorption and size relationships were used to categorize black carbon and dust as dominant absorbers and to identify a third category in which both black carbon and dust dominate absorption. Moderate Resolution Imaging Spectroradiometer (MODIS) AOD retrievals with the lowest quality assurance (QA ≥ 0) flags were biased high with respect to TIGERZ IOP area-averaged measurements. MODIS AOD retrievals with QA ≥ 0 had moderate correlation (R2 = 0.52-0.69) with the Kanpur AERONET site, whereas retrievals with QA > 0 were limited in number. Mesoscale-distributed Sun photometers quantified temporal and spatial variability of aerosol properties, and these results were used to validate satellite retrievals.

  15. Observed changes in aerosol physical and optical properties before and after precipitation events

    NASA Astrophysics Data System (ADS)

    Li, Xingmin; Dong, Yan; Dong, Zipeng; Du, Chuanli; Chen, Chuang

    2016-08-01

    Precipitation scavenging of aerosol particles is an important removal process in the atmosphere that can change aerosol physical and optical properties. This paper analyzes the changes in aerosol physical and optical properties before and after four rain events using in situ observations of mass concentration, number concentration, particle size distribution, scattering and absorption coefficients of aerosols in June and July 2013 at the Xianghe comprehensive atmospheric observation station in China. The results show the effect of rain scavenging is related to the rain intensity and duration, the wind speed and direction. During the rain events, the temporal variation of aerosol number concentration was consistent with the variation in mass concentration, but their size-resolved scavenging ratios were different. After the rain events, the increase in aerosol mass concentration began with an increase in particles with diameter <0.8 μm [measured using an aerodynamic particle sizer (APS)], and fine particles with diameter <0.1 μm [measured using a scanning mobility particle sizer (SMPS)]. Rainfall was most efficient at removing particles with diameter ~0.6 μm and greater than 3.5 μm. The changes in peak values of the particle number distribution (measured using the SMPS) before and after the rain events reflect the strong scavenging effect on particles within the 100-120 nm size range. The variation patterns of aerosol scattering and absorption coefficients before and after the rain events were similar, but their scavenging ratios differed, which may have been related to the aerosol particle size distribution and chemical composition.

  16. Scattering and Absorption of E&M radiation by small particles-applications to study impact of biomass aerosols on climate

    NASA Astrophysics Data System (ADS)

    Bililign, Solomon; Singh, Sujeeta; Fiddler, Marc; Smith, Damon

    2015-03-01

    The phenomena of scattering, absorption, and emission of light and other electromagnetic radiation by small particles are central to many science and engineering disciplines. Absorption of solar radiation by black carbon aerosols has a significant impact on the atmospheric energy distribution and hydrologic processes. By intercepting incoming solar radiation before it reaches the surface, aerosols heat the atmosphere and, in turn, cool the surface. The magnitude of the atmospheric forcing induced by anthropogenic absorbing aerosols, mainly black carbon (BC) emitted from biomass burning and combustion processes has been suggested to be comparable to the atmospheric forcing by all greenhouse gases (GHGs). Despite the global abundance of biomass burning for cooking, forests clearing for agriculture and wild fires, the optical properties of these aerosols have not been characterized at wide range of wavelengths. Our laboratory uses a combination of Cavity ring down spectroscopy and integrating nephelometry to measure optical properties of (extinction, absorption and scattering coefficients) of biomass aerosols. Preliminary results will be presented. Supported by the Department of Defense under Grant #W911NF-11-1-0188.

  17. An investigation of aerosol optical properties: Atmospheric implications and influences

    NASA Astrophysics Data System (ADS)

    Penaloza-Murillo, Marcos A.

    An experimental, observational, and theoretical investigation of aerosol optical properties has been made in this work to study their implications and influences on the atmosphere. In the laboratory the scientific and instrumental methodology consisted of three parts, namely, aerosol generation, optical and mass concentration measurements, and computational calculations. In particular the optical properties of ammonium sulfate and caffeine aerosol were derived from measurements made with a transmissometer cell-reciprocal- integrating nephelometer (TCRIN), equipped with a laser beam at 632.8 nm, and by applying a Mie theory computer code The aerosol generators, optical equipment and calibration procedures were reviewed. The aerosol shape and size distribution were studied by means of scanning electron microscopy and the Gumprecht- Sliepcevich/Lipofsky-Green extinction-sedimentation method. In particular the spherical and cylindrical shape were considered. During this investigation, an alternative method for obtaining the optical properties of monodisperse spherical non-absorbing aerosol using a cell-transmissometer, which is based on a linearisation of the Lambert-Beer law, was found. In addition, adapting the TCRIN to electrooptical aerosol studies, the optical properties of a circular-cylindrical aerosol of caffeine were undertaken under the condition of random orientation in relation with the laser beam, and perpendicular orientation to it. A theoretical study was conducted to assess the sensitivity of aerosol to a change of shape under different polarisation modes. The aerosol optical properties, obtained previously in the laboratory, were then used to simulate the direct radiative forcing. The calculations and results were obtained by applying a one- dimensional energy-balance box model. The influence of atmospheric aerosol on the sky brightness due to a total solar eclipse was studied using the photometric and meteorological observations made during the

  18. Aerosol activation properties and CCN closure during TCAP

    NASA Astrophysics Data System (ADS)

    Mei, F.; Tomlinson, J. M.; Shilling, J. E.; Wilson, J. M.; Zelenyuk, A.; Chand, D.; Comstock, J. M.; Hubbe, J.; Berg, L. K.; Schmid, B.

    2013-12-01

    The indirect effects of atmospheric aerosols currently remain the most uncertain components in forcing of climate change over the industrial period (IPCC, 2007). This large uncertainty is partially due to our incomplete understanding of the ability of particles to form cloud droplets under atmospherically relevant supersaturation. In addition, there is a large uncertainty in the aerosol optical depth (AOD) simulated by climate models near the North American coast and a wide variety in the types of clouds are observed over this region. The goal of the US Department of Energy Two Column Aerosol Project (TCAP) is to understand the processes responsible for producing and maintaining aerosol distributions and associated radiative and cloud forcing off the coast of North America. During the TCAP study, aerosol total number concentration, cloud condensation nuclei (CCN) spectra and aerosol chemical composition were in-situ measured from the DOE Gulfstream 1 (G-1) research aircraft during two Intensive Operations Periods (IOPs), one conducted in July 2012 and the other in February 2013. An overall aerosol size distribution was achieved by merging the observations from several instruments, including Ultra High Sensitivity Aerosol Spectrometer - Airborne (UHSAS-A, DMT), Passive Cavity Aerosol Spectrometer Probe (PCASP-200, DMT), and Cloud Aerosol Spectrometer (CAS, DMT). Aerosol chemical composition was characterized using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS, Aerodyne Inc.) and single particle mass spectrometer, mini-SPLAT. Based on the aerosol size distribution, CCN number concentration (characterized by a DMT dual column CCN counter with a range from 0.1% to 0.4%), and chemical composition, a CCN closure was obtained. The sensitivity of CCN closure to organic hygroscopicity was investigated. The differences in aerosol/CCN properties between two columns, and between two phases, will be discussed.

  19. Quantitative retrieval of aerosol optical properties by means of ceilometers

    NASA Astrophysics Data System (ADS)

    Wiegner, Matthias; Gasteiger, Josef; Geiß, Alexander

    2016-04-01

    In the last few years extended networks of ceilometers have been established by several national weather services. Based on improvements of the hardware performance of these single-wavelength backscatter lidars and their 24/7 availability they are increasingly used to monitor mixing layer heights and to derive profiles of the particle backscatter profile. As a consequence they are used for a wide range of applications including the dispersion of volcanic ash plumes, validation of chemistry transport models and air quality studies. In this context the development of automated schemes to detect aerosol layers and to identify the mixing layer are essential, in particular as the latter is often used as a proxy for air quality. Of equal importance is the calibration of ceilometer signals as a pre-requisite to derive quantitative optical properties. Recently, it has been emphasized that the majority of ceilometers are influenced by water vapor absorption as they operate in the spectral range of 905 - 910 nm. If this effect is ignored, errors of the aerosol backscatter coefficient can be as large as 50%, depending on the atmospheric water vapor content and the emitted wavelength spectrum. As a consequence, any other derived quantity, e.g. the extinction coefficient or mass concentration, would suffer from a significant uncertainty in addition to the inherent errors of the inversion of the lidar equation itself. This can be crucial when ceilometer derived profiles shall be used to validate transport models. In this presentation, the methodology proposed by Wiegner and Gasteiger (2015) to correct for water vapor absorption is introduced and discussed.

  20. Satellite-Based Evidence of Wavelength-Dependent Aerosol Absorption in Biomass Burning Smoke Inferred from Ozone Monitoring Instrument

    NASA Technical Reports Server (NTRS)

    Jethva, H.; Torres, O.

    2012-01-01

    We provide satellite-based evidence of the spectral dependence of absorption in biomass burning aerosols over South America using near-UV measurements made by the Ozone Monitoring Instrument (OMI) during 2005-2007. In the current near-UV OMI aerosol algorithm (OMAERUV), it is implicitly assumed that the only absorbing component in carbonaceous aerosols is black carbon whose imaginary component of the refractive index is wavelength independent. With this assumption, OMI-derived aerosol optical depth (AOD) is found to be significantly over-estimated compared to that of AERONET at several sites during intense biomass burning events (August-September). Other well-known sources of error affecting the near-UV method of aerosol retrieval do not explain the large observed AOD discrepancies between the satellite and the ground-based observations. A number of studies have revealed strong spectral dependence in carbonaceous aerosol absorption in the near-UV region suggesting the presence of organic carbon in biomass burning generated aerosols. A sensitivity analysis examining the importance of accounting for the presence of wavelength-dependent aerosol absorption in carbonaceous particles in satellite-based remote sensing was carried out in this work. The results convincingly show that the inclusion of spectrally-dependent aerosol absorption in the radiative transfer calculations leads to a more accurate characterization of the atmospheric load of carbonaceous aerosols.

  1. Overview of ACE-Asia Spring 2001 Investigations on Aerosol Radiative Effects and Related Aerosol Properties

    NASA Technical Reports Server (NTRS)

    Russell, Philip B.; Valero, F. P. J.; Flatau, P. J.; Bergin, M.; Holben, B.; Nakajima, T.; Pilewskie, P.; Bergstrom, R.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    A primary, ACE-Asia objective was to quantify the interactions between aerosols and radiation in the Asia-Pacific region. Toward this end, radiometric and related aerosol measurements were made from ocean, land, air and space platforms. Models that predict aerosol fields guided the measurements and are helping integrate and interpret results. Companion overview's survey these measurement and modeling components. Here we illustrate how these components were combined to determine aerosol radiative. impacts and their relation to aerosol properties. Because clouds can obscure or change aerosol direct radiative effects, aircraft and ship sorties to measure these effects depended on predicting and finding cloud-free areas and times with interesting aerosols present. Pre-experiment satellite cloud climatologies, pre-flight aerosol and cloud forecasts, and in-flight guidance from satellite imagery all helped achieve this. Assessments of aerosol regional radiative impacts benefit from the spatiotemporal coverage of satellites, provided satellite-retrieved aerosol properties are accurate. Therefore, ACE-Asia included satellite retrieval tests, as part of many comparisons to judge the consistency (closure) among, diverse measurements. Early results include: (1) Solar spectrally resolved and broadband irradiances and optical depth measurements from the C-130 aircraft and at Kosan, Korea yielded aerosol radiative forcing efficiencies, permitting comparisons between efficiencies of ACE-Asia and INDOEX aerosols, and between dust and "pollution" aerosols. Detailed results will be presented in separate papers. (2) Based on measurements of wavelength dependent aerosol optical depth (AOD) and single scattering albedo the estimated 24-h a average aerosol radiative forcing efficiency at the surface for photosynthetically active radiation (400 - 700 nm) in Yulin, China is approx. 30 W sq m per AOD(500 nm). (3) The R/V Brown cruise from Honolulu to Sea of Japan sampled an aerosol optical

  2. Statistical Estimation of the Atmospheric Aerosol Absorption Coefficient Based on the Data of Optical Measurements

    SciTech Connect

    Uzhegov, V.N.; Kozlov, V.S.; Panchenko, M.V.; Pkhalagov, Yu.A.; Pol'kin, V.V.; Terpugova, S.A.; Shmargunov, V.P.; Yausheva, E.P.

    2005-03-18

    The problem of the choice of the aerosol optical constants and, in particular, imaginary part of the refractive index of particles in visible and infrared (IR) wavelength ranges is very important for calculation of the global albedo of the atmosphere in climatic models. The available models of the aerosol optical constants obtained for the prescribed chemical composition of particles (see, for example, Ivlev et al. 1973; Ivlev 1982; Volz 1972), often are far from real aerosol. It is shown in (Krekov et al. 1982) that model estimates of the optical characteristics of the atmosphere depending on the correctness of real and imaginary parts of the aerosol complex refractive index can differ by some hundreds percent. It is known that the aerosol extinction coefficient {alpha}({lambda}) obtained from measurements on a long horizontal path can be represented as {alpha}({lambda})={sigma}({lambda})+{beta}({lambda}), where {sigma} is the directed light scattering coefficient, and {beta} is the aerosol absorption coefficient. The coefficient {sigma}({lambda}) is measured by means of a nephelometer. Seemingly, if measure the values {alpha}({lambda}) and {sigma}({lambda}), it is easy to determine the value {beta}({lambda}). However, in practice it is almost impossible for a number of reasons. Firstly, the real values {alpha}({lambda}) and {sigma}({lambda}) are very close to each other, and the estimate of the parameter {beta}({lambda}) is concealed by the errors of measurements. Secondly, the aerosol optical characteristics on the long path and in the local volume of nephelometer can be different, that also leads to the errors in estimating {beta}({lambda}). Besides, there are serious difficulties in performing spectral measurements of {sigma}({lambda}) in infrared wavelength range. Taking into account these circumstances, in this paper we consider the statistical technique, which makes it possible to estimate the absorption coefficient of real aerosol on the basis of analysis

  3. Aerosol Absorption Above Clouds from Combined OMI and MODIS Hyperspectral Measurements

    NASA Astrophysics Data System (ADS)

    de Graaf, M.; Tilstra, L. G.; Stammes, P.

    2015-06-01

    The aerosol direct effect (DRE) over clouds from combined OMI and MODIS hyperspectral measurements is presented. The radiative effect of UV-absorbing aerosols can be retrieved with high accuracy, using hyperspectral measurements and simulated clean cloud spectra. Since SCIAMACHY was lost in 2012, we use new measurements from OMI and MODIS to continue the observation of aerosol absorption over clouds from space. Each instrument by itself does not provide enough information on both aerosols and clouds, but OMI gives detailed information of UV aerosol absorption, while MODIS’ broadband channels provide cloud information from the SWIR range of the spectrum. OMI and MODIS are flying in formation in the A-Train constellation, providing observations about 8-15 minutes after one another. This creates uncertainties in the observed scene, especially in scenes where convection is strong and cloud parameters change rapidly. However, OMI and MODIS overlap at MODIS’ smallest wavelength band, 469 nm, which can be used to test the matching of the spectra. Furthermore, MODIS provides cloud products at 1 Å~ 1 km resolution, and better, which can be used to test and improve the cloud retrieval algorithmthat was developed for the much larger SCIAMACHY and OMI pixels. Application of this unique method to OMI andMODIS is used to prepare for TROPOMI, which will provide information on both the UV and the SWIR with an unprecedented accuracy and unprecedented spatial resolution.

  4. Aerosol scattering and absorption during the EUCAARI-LONGREX flights of the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146: can measurements and models agree?

    NASA Astrophysics Data System (ADS)

    Highwood, E. J.; Northway, M. J.; McMeeking, G. R.; Morgan, W. T.; Liu, D.; Osborne, S.; Bower, K.; Coe, H.; Ryder, C.; Williams, P.

    2012-08-01

    Scattering and absorption by aerosol in anthropogenically perturbed air masses over Europe has been measured using instrumentation flown on the UK's BAe-146-301 large Atmospheric Research Aircraft (ARA) operated by the Facility for Airborne Atmospheric Measurements (FAAM) on 14 flights during the EUCAARI-LONGREX campaign in May 2008. The geographical and temporal variations of the derived shortwave optical properties of aerosol are presented. Values of single scattering albedo of dry aerosol at 550 nm varied considerably from 0.86 to near unity, with a campaign average of 0.93 ± 0.03. Dry aerosol optical depths ranged from 0.030 ± 0.009 to 0.24 ± 0.07. An optical properties closure study comparing calculations from composition data and Mie scattering code with the measured properties is presented. Agreement to within measurement uncertainties of 30% can be achieved for both scattering and absorption, but the latter is shown to be sensitive to the refractive indices chosen for organic aerosols, and to a lesser extent black carbon, as well as being highly dependent on the accuracy of the absorption measurements. Agreement with the measured absorption can be achieved either if organic carbon is assumed to be weakly absorbing, or if the organic aerosol is purely scattering and the absorption measurement is an overestimate due to the presence of large amounts of organic carbon. Refractive indices could not be inferred conclusively due to this uncertainty, despite the enhancement in methodology compared to previous studies that derived from the use of the black carbon measurements. Hygroscopic growth curves derived from the wet nephelometer indicate moderate water uptake by the aerosol with a campaign mean f(RH) value (ratio in scattering) of 1.5 (range from 1.23 to 1.63) at 80% relative humidity. This value is qualitatively consistent with the major chemical components of the aerosol measured by the aerosol mass spectrometer, which are primarily mixed organics and

  5. Light absorption properties and absorption budget of Southeast Pacific waters

    NASA Astrophysics Data System (ADS)

    Bricaud, Annick; Babin, Marcel; Claustre, Hervé; Ras, JoséPhine; TièChe, Fanny

    2010-08-01

    Absorption coefficients of phytoplankton, nonalgal particles (NAPs), and colored dissolved organic matter (CDOM), and their relative contributions to total light absorption, are essential variables for bio-optical and biogeochemical models. However, their actual variations in the open ocean remain poorly documented, particularly for clear waters because of the difficulty in measuring very low absorption coefficients. The Biogeochemistry and Optics South Pacific Experiment (BIOSOPE) cruise investigated a large range of oceanic regimes, from mesotrophic waters around the Marquesas Islands to hyperoligotrophic waters in the subtropical gyre and eutrophic waters in the upwelling area off Chile. The spectral absorption coefficients of phytoplankton and NAPs were determined using the filter technique, while the CDOM absorption coefficients were measured using a 2 m capillary waveguide. Over the whole transect, the absorption coefficients of both dissolved and particulate components covered approximately two orders of magnitude; in the gyre, they were among the lowest ever reported for open ocean waters. In the oligotrophic and mesotrophic waters, absorption coefficients of phytoplankton and NAPs were notably lower than those measured in other oceanic areas with similar chlorophyll contents, indicating some deviation from the standard chlorophyll-absorption relationships. The contribution of absorption by NAPs to total particulate absorption showed large vertical and horizontal variations. CDOM absorption coefficients covaried with algal biomass, albeit with a high scatter. The spectral slopes of both NAP and CDOM absorption revealed structured spatial variability in relation with the trophic conditions. The relative contributions of each component to total nonwater absorption were (at a given wavelength) weakly variable over the transect, at least within the euphotic layer.

  6. Aerosol Optical Properties in Southeast Asia From AERONET Observations

    NASA Astrophysics Data System (ADS)

    Eck, T. F.; Holben, B. N.; Boonjawat, J.; Le, H. V.; Schafer, J. S.; Reid, J. S.; Dubovik, O.; Smirnov, A.

    2003-12-01

    There is little published data available on measured optical properties of aerosols in the Southeast Asian region. The AERONET project and collaborators commenced monitoring of aerosol optical properties in February 2003 at four sites in Thailand and two sites in Viet Nam to measure the primarily anthropogenic aerosols generated by biomass burning and fossil fuel combustion/ industrial emissions. Automatic sun/sky radiometers at each site measured spectral aerosol optical depth in 7 wavelengths from 340 to 1020 nm and combined with directional radiances in the almucantar, retrievals were made of spectral single scattering albedo and aerosol size distributions. Angstrom exponents, size distributions and spectral single scattering albedo of primarily biomass burning aerosols at rural sites are compared to measurements made at AERONET sites in other major biomass burning regions in tropical southern Africa, South America, and in boreal forest regions. Additionally, the aerosol single scattering albedo and size distributions measured in Bangkok, Thailand are compared with those measured at other urban sites globally. The influences of aerosols originating from other regions outside of Southeast Asia are analyzed using trajectory analyses. Specifically, cases of aerosol transport and mixing from Southern China and from India are presented.

  7. A study of aerosol optical properties using a lightweight optical particle spectrometer and sun photometer from an unmanned aerial system

    NASA Astrophysics Data System (ADS)

    Telg, H.; Murphy, D. M.; Bates, T. S.; Johnson, J. E.; Gao, R. S.

    2015-12-01

    A miniaturized printed optical particle spectrometer (POPS) and sun photometer (miniSASP) have been developed recently for unmanned aerial systems (UAS) and balloon applications. Here we present the first scientific data recorded by the POPS and miniSASP from a Manta UAS during a field campaign on Svalbard, Norway, in April 2015. As part of a payload composed of five different aerosol instruments (absorption photometer, condensation particle counter, filter sampler, miniSASP and POPS) we collected particle size distributions, the optical depth (OD) and the sky brightness from 0 to 3000 m altitude. The complementary measurement approaches of the miniSASP and POPS allow us to calculate aerosol optical properties such as the aerosol optical depth and the angstrom exponent or the asymmetry parameter independently. We discuss deviation between results with respect to aerosol properties, e.g. hygroscopicity and absorption, as well as instrumental limitations.

  8. Regional aerosol properties: Comparisons of boundary layer measurements from ACE 1, ACE 2, Aerosols99, INDOEX, ACE Asia, TARFOX, and NEAQS

    NASA Astrophysics Data System (ADS)

    Quinn, Patricia K.; Bates, Timothy S.

    2005-07-01

    Means and variability of aerosol chemical composition and optical properties are compared for the first and second Aerosol Characterization Experiments (ACE 1 and ACE 2), a cruise across the Atlantic (Aerosols99), the Indian Ocean Experiment (INDOEX), the Asian Aerosol Characterization Experiment (ACE Asia), the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX), and the New England Air Quality Study (NEAQS). These experiments were focused either on the remote marine atmosphere (ACE 1) or areas downwind of continental aerosol source regions including western Europe, North America, Africa, India, and Asia. Presented here are size-segregated concentrations of aerosol mass, sea salt, non-sea-salt (nss) SO4=, NH4+, NO3-, dust, organic carbon (OC), elemental carbon (EC), and nss K+, as well as mass ratios that are commonly used to identify aerosol sources and to assess aerosol processing (Cl- to Na+, OC to nss SO4=, EC to total carbon (TC), EC to nss SO4=, nss K+ to EC, Fe to Al, and Si to Al). Optical properties that are compared include size-segregated scattering, backscattering, and absorption coefficients, and single-scattering albedo at 550 nm. Size-segregated mass scattering and mass absorption efficiencies for the total aerosol and mass extinction efficiencies for the dominant chemical components also are compared. In addition, we present the contribution to light extinction by the dominant chemical components for each region. All data are based on shipboard measurements performed at a relative humidity of 55 ± 5%. Scattering coefficients and single-scattering albedos also are reported at ambient relative humidity (RH) using published values of f(RH). Finally, aerosol optical depths from each region are compared. Identical sampling protocols were used in all experiments in order to eliminate sampling biases and to make the data directly comparable. Major findings include (1) nss SO4= makes up only 16 to 46% of the submicron aerosol mass

  9. Comparison of three methods for measuring light absorption by collected aerosols.

    PubMed

    Ramsey-Bell, D C; Couture, G

    1985-08-01

    Three instruments for measuring absorption of visible light by atmospheric aerosols are compared: the visual comparator; plate diffuser; and photoacoustic spectrometer. Two versions of the photoacoustic spectrometer are tested, one built of acrylic plastic and the other of aluminum. One version of the visual comparator uses Millipore filters for a crucial reflective surface, another a mirror. Several materials collected on Nuclepore filters are used in the comparison. Laboratory generated samples consist of carbon and carbon overlaid with ammonium sulfate. Atmospheric aerosols were collected in Tucson and on an Arizona mountain peak. All methods give reasonably consistent results, even when applied to the lightly absorbing nonurban atmospheric samples. PMID:18223896

  10. Uncertainties of simulated aerosol optical properties induced by assumptions on aerosol physical and chemical properties: an AQMEII-2 perspective

    EPA Science Inventory

    The calculation of aerosol optical properties from aerosol mass is a process subject to uncertainty related to necessary assumptions on the treatment of the chemical species mixing state, density, refractive index, and hygroscopic growth. In the framework of the AQMEII-2 model in...

  11. Estimating aerosol light-scattering enhancement from dry aerosol optical properties at different sites

    NASA Astrophysics Data System (ADS)

    Titos, Gloria; Jefferson, Anne; Sheridan, Patrick; Andrews, Elisabeth; Lyamani, Hassan; Ogren, John; Alados-Arboledas, Lucas

    2014-05-01

    Microphysical and optical properties of aerosol particles are strongly dependent on the relative humidity (RH). Knowledge of the effect of RH on aerosol optical properties is of great importance for climate forcing calculations and for comparison of in-situ measurements with satellite and remote sensing retrievals. The scattering enhancement factor, f(RH), is defined as the ratio of the scattering coefficient at a high and reference RH. Predictive capability of f(RH) for use in climate models would be enhanced if other aerosol parameters could be used as proxies to estimate hygroscopic growth. Toward this goal, we explore the relationship between aerosol light-scattering enhancement and dry aerosol optical properties such as the single scattering albedo (SSA) and the scattering Ångström exponent (SAE) at multiple sites around the world. The measurements used in this study were conducted by the US Department of Energy at sites where different aerosol types predominate (pristine marine, polluted marine, dust dominated, agricultural and forest environments, among others). In all cases, the scattering enhancement decreases as the SSA decreases, that is, as the contribution of absorbing particles increases. On the other hand, for marine influenced environments the scattering enhancement clearly increases as the contribution of coarse particles increases (SAE decreases), evidence of the influence of hygroscopic coarse sea salt particles. For other aerosol types the relationship between f(RH) and SAE is not so straightforward. Combining all datasets, f(RH) was found to exponentially increase with SSA with a high correlation coefficient.

  12. Assessment of aerosol optical property and radiative effect for the layer decoupling cases over the northern South China Sea during the 7-SEAS/Dongsha Experiment

    NASA Astrophysics Data System (ADS)

    Pani, Shantanu Kumar; Wang, Sheng-Hsiang; Lin, Neng-Huei; Tsay, Si-Chee; Lolli, Simone; Chuang, Ming-Tung; Lee, Chung-Te; Chantara, Somporn; Yu, Jin-Yi

    2016-05-01

    The aerosol radiative effect can be modulated by the vertical distribution and optical properties of aerosols, particularly when aerosol layers are decoupled. Direct aerosol radiative effects over the northern South China Sea (SCS) were assessed by incorporating an observed data set of aerosol optical properties obtained from the Seven South East Asian Studies (7-SEAS)/Dongsha Experiment into a radiative transfer model. Aerosol optical properties for a two-layer structure of aerosol transport were estimated. In the radiative transfer calculations, aerosol variability (i.e., diversity of source region, aerosol type, and vertical distribution) for the complex aerosol environment was also carefully quantified. The column-integrated aerosol optical depth (AOD) at 500 nm was 0.1-0.3 for near-surface aerosols and increased 1-5 times in presence of upper layer biomass-burning aerosols. A case study showed the strong aerosol absorption (single-scattering albedo (ω) ≈ 0.92 at 440 nm wavelength) exhibited by the upper layer when associated with predominantly biomass-burning aerosols, and the ω (≈0.95) of near-surface aerosols was greater than that of the upper layer aerosols because of the presence of mixed type aerosols. The presence of upper level aerosol transport could enhance the radiative efficiency at the surface (i.e., cooling) and lower atmosphere (i.e., heating) by up to -13.7 and +9.6 W m-2 per AOD, respectively. Such enhancement could potentially modify atmospheric stability, can influence atmospheric circulation, as well as the hydrological cycle over the tropical and low-latitude marginal northern SCS.

  13. Mid- and far-infrared absorption spectroscopy of Titan’s aerosols analogues

    NASA Astrophysics Data System (ADS)

    Gautier, Thomas; Carrasco, Nathalie; Mahjoub, Ahmed; Vinatier, Sandrine; Giuliani, Alexandre; Szopa, Cyril; Anderson, Carrie M.; Correia, Jean-Jacques; Dumas, Paul; Cernogora, Guy

    2012-09-01

    In this work we present mid- and far-infrared absorption spectra of Titan’s aerosol analogues produced in the PAMPRE experimental setup. The evolution of the linear absorption coefficient ε (cm-1) is given as a function of the wavenumber. We provide a complete dataset regarding the influence that the concentration of methane vapor in the gas mixture has on the tholin spectra. Among other effects, the intensity of the 2900 cm-1 (3.4 μm) pattern (attributed to methyl stretching modes) increases when the methane concentration increases. More generally, tholins produced with low methane concentrations seem to be more amine based polymers, whereas tholins produced with higher methane concentrations contains more aliphatic carbon based structures. Moreover, it is shown that the position of the bands around 2900 cm-1 depends on the chemical environment of the methyl functional group. We conclude that the presence of these absorption bands in Titan’s atmosphere, as measured with the VIMS instrument onboard Cassini is in agreement with an aerosol contribution. We also compare the far-infrared spectrum of tholin to spectra of Titan’s aerosols derived from recent Cassini-CIRS observations displaying many similarities, particularly with absorption bands at 325 cm-1, 515 cm-1, and the methyl attributed 1380 cm-1 and 1450 cm-1 bands.

  14. Enhanced UV Absorption in Carbonaceous Aerosols during MILAGRO and Identification of Potential Organic Contributors.

    NASA Astrophysics Data System (ADS)

    Mangu, A.; Kelley, K. L.; Marchany-Rivera, A.; Kilaparty, S.; Gunawan, G.; Gaffney, J. S.; Marley, N. A.

    2007-12-01

    Measurements of aerosol absorption were obtained as part of the MAX-Mex component of the MILAGRO field campaign at site T0 (Instituto Mexicano de Petroleo in Mexico City) during the month of March, 2006 by using a 7- channel aethalometer (Thermo-Anderson). These measurements, obtained at 370, 470, 520, 590, 660, 880, and 950 nm at a 5 minute time resolution, showed an enhanced absorption in the UV over that expected from carbon soot alone. Samples of fine atmospheric aerosols (less than 0.1micron) were also collected at site T0 and T1 (Universidad Technologica de Tecamac, State of Mexico) from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. The samples were collected on quartz fiber filters with high volume impactor samplers. The samples have been characterized for total carbon content (stable isotope ratio mass spectroscopy) and natural radionuclide tracers (210Pb, 210Po, 210Bi, 7Be, 13C, 14C, 40K, 15N). Continuous absorption spectra of these aerosol samples have been obtained in the laboratory from 280 to 900nm with the use of an integrating sphere coupled to a UV-visible spectrometer (Beckman DU with a Labsphere accessory). The integrating sphere allows the detector to collect and spatially integrate the total radiant flux reflected from the sample and therefore allows for the measurement of absorption on highly reflective or diffusely scattering samples (1). The continuous spectra also show an enhanced UV absorption over that expected from carbon soot and the general profiles are quite similar to those observed for humic and fulvic acids found as colloidal materials in surface and groundwaters (2), indicating the presence of humic-like substances (HULIS) in the fine aerosols. The spectra also show evidence of narrow band absorbers below 400 nm typical of polycyclic aromatics (PAH) and nitrated aromatic compounds. Spectra were also obtained on NIST standard diesel soot (SRM 2975), NIST standard air particulate matter (SRM 8785

  15. Sensitivity of spectral reflectance to aerosol optical properties in UV and visible wavelength range: Preparatory study for aerosol retrieval from Geostationary Environmental Monitoring Spectrometer (GEMS)

    NASA Astrophysics Data System (ADS)

    KIM, M.; Kim, J.; Lee, J.

    2011-12-01

    Asia, with its rapid increase in industrialization and population, has been receiving great attention as one of important source regions of pollutants including aerosols and trace gases. Since the spatio-temporal distribution of the pollutants varies rapidly, demands to monitor air quality in a geostationary satellite have increased recently. In these perspectives, the Ministry of Environment of Korea initiated a geostationary satellite mission to launch the Geostationary Environmental Monitoring Spectrometer (GEMS) onboard the GEO-KOMPSAT in 2017-2018 timeframe. From the Ozone Monitoring Instrument (OMI) measurements, it has been found that the low surface reflectance and strong interaction between aerosol absorption and molecular scattering in UV wavelength range can be advantageous in retrieving aerosol optical properties, such as aerosol optical thickness (AOT) and optical type (or single scattering albedo), over the source regions as well as ocean areas. In addition, GEMS is expected to have finer spatial resolution compared to OMI (13 x 24 km2 at nadir), thereby less affected by sub-pixel clouds. In this study, we present sensitivity of spectral reflectance to aerosol optical properties in ultraviolet (UV) and visible wavelength range for a purpose to retrieve aerosol optical properties from GEMS. The so called UV-VIS algorithm plans to use spectral reflectance in 350-650 nm. The algorithm retrieves AOT and aerosol type using an inversion method, which adopts pre-calculated lookup table (LUT) for a set of assumed aerosol models. For the aerosol models optimized in Asia areas, the inversion data of Aerosol Robotic Network (AERONET) located in the target areas are selectively used to archive aerosol optical properties. As a result, major aerosol types representing dust, polluted dust, and absorbing/non-absorbing anthropogenic aerosols are constructed and used for the LUT calculations. We analyze the effect of cloud contamination on the retrieved AOT by

  16. Absorption of Visible and Long-wave Radiation by Primary and Secondary Biogenic Aerosols.

    NASA Astrophysics Data System (ADS)

    Gaffney, J. S.; Marley, N. A.

    2008-12-01

    Field results for the 14C content of carbonaceous aerosols are presented that indicate significant biogenic sources of both primary and secondary aerosols in urban and regional environments. Samples collected in Mexico City and downwind of the urban area during the MILAGRO field study are compared with results reported previously in the literature indicating a significant amount of biogenic aerosols from both biomass burning and secondary photochemical production (e.g. terpene oxidations) are contributing to the overall carbonaceous aerosols in the optically active region of 0.1 to 1.0 micron. Samples in this size range collected on quartz fiber filters were also examined using an integrating sphere and FTIR diffuse reflectance techniques to obtain absorption spectra from 280 to the mid-IR. These data clearly indicate that the biogenic derived primary aerosols from agricultural and trash-burning, as well as secondary organic aerosols from isoprene and terpene oxidations will produce both UV-Visible (short-wave) absorbing substances as well as IR (long-wave) absorbing compounds including humic-like-substances (HULIS). With the anticipated increases in growing seasons (i.e. earlier springs and longer summers) the likely hood of increased fires (forest and grassland) as well as the continuing growth in agricultural burning activities, these primary sources are expected to increase and may play a role in heating of the atmosphere. The compound effects of these primary and secondary biogenic sources of absorbing aerosols to the total aerosol loading and regional climate will be discussed. This work was supported by the Office of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-07ER64328 as part of the Atmospheric Science Program.

  17. Physico-chemical properties of aerosols in Sao Paulo, Brazil and mechanisms of secondary organic aerosol formation.

    NASA Astrophysics Data System (ADS)

    Artaxo, Paulo; Ferreira de Brito, Joel; Varanda Rizzo, Luciana; Luiza Godoy, Maria; Godoy, Jose Marcus

    2013-04-01

    Megacities emissions are increasingly becoming a global issue, where emissions from the transportation sector play an increasingly important role. Sao Paulo is a megacity with a population of about 18 million people, 7 million cars and large-scale industrial emissions. As a result of the vehicular and industrial emissions, the air quality in Sao Paulo is bellow WMO standards for aerosol particles and ozone. Many uncertainties are found on gas- and particulate matter vehicular emission factors and their following atmospheric processes, e.g. secondary organic aerosol formation. Due to the uniqueness of the vehicular fuel in Brazil, largely based on ethanol use, such characterization currently holds further uncertainties. To improve the understanding of the role of this unique emission characteristics, we are running a source apportionment study in Sao Paulo focused on the mechanisms of organic aerosol formation. One of the goals of this study is a quantitative aerosol source apportionment focused on vehicular emissions, including ethanol and gasohol (both fuels used by light-duty vehicles). This study comprises four sampling sites with continuous measurements for one year, where trace elements and organic aerosol are being measured for PM2.5 and PM10 along with real-time NOx, O3, PM10 and CO measurements. Aerosol optical properties and size distribution are being measured on a rotation basis between sampling stations. Furthermore, a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) and an Aerosol Chemical Speciation Monitor (ACSM) are used to measure in real time VOCs and aerosol composition, respectively. Trace elements were measured using XRF and OC/EC analysis was determined with a Sunset OC/EC instrument. A TSI Nephelometer with 3 wavelengths measure light scattering and a MAAP measure black carbon. Results show aerosol number concentrations ranging between 10,000 and 35,000 cm-3, mostly concentrated in the nucleation and Aitken modes, with a peak in size at 80

  18. Evaluating Global Aerosol Models and Aerosol and Water Vapor Properties Near Clouds

    SciTech Connect

    Turner, David, D.; Ferrare, Richard, A.

    2011-07-06

    The 'Evaluating Global Aerosol Models and Aerosol and Water Vapor Properties Near Clouds' project focused extensively on the analysis and utilization of water vapor and aerosol profiles derived from the ARM Raman lidar at the Southern Great Plains ARM site. A wide range of different tasks were performed during this project, all of which improved quality of the data products derived from the lidar or advanced the understanding of atmospheric processes over the site. These activities included: upgrading the Raman lidar to improve its sensitivity; participating in field experiments to validate the lidar aerosol and water vapor retrievals; using the lidar aerosol profiles to evaluate the accuracy of the vertical distribution of aerosols in global aerosol model simulations; examining the correlation between relative humidity and aerosol extinction, and how these change, due to horizontal distance away from cumulus clouds; inferring boundary layer turbulence structure in convective boundary layers from the high-time-resolution lidar water vapor measurements; retrieving cumulus entrainment rates in boundary layer cumulus clouds; and participating in a field experiment that provided data to help validate both the entrainment rate retrievals and the turbulent profiles derived from lidar observations.

  19. Polarization of skylight in the O(2)A band: effects of aerosol properties.

    PubMed

    Boesche, Eyk; Stammes, Piet; Preusker, Réne; Bennartz, Ralf; Knap, Wouter; Fischer, Juergen

    2008-07-01

    Motivated by several observations of the degree of linear polarization of skylight in the oxygen A (O(2)A) band that do not yet have a quantitative explanation, we analyze the influence of aerosol altitude, microphysics, and optical thickness on the degree of linear polarization of the zenith skylight in the spectral region of the O(2)A band, between 755 to 775 nm. It is shown that the degree of linear polarization inside the O(2)A band is particularly sensitive to aerosol altitude. The sensitivity is strongest for aerosols within the troposphere and depends also on their microphysical properties and optical thickness. The polarization of the O(2)A band can be larger than the polarization of the continuum, which typically occurs for strongly polarizing aerosols in an elevated layer, or smaller, which typically occurs for depolarizing aerosols or cirrus clouds in an elevated layer. We show that in the case of a single aerosol layer in the atmosphere a determination of the aerosol layer altitude may be obtained. Furthermore, we show limitations of the aerosol layer altitude determination in case of multiple aerosol layers. To perform these simulations we developed a fast method for multiple scattering radiative transfer calculations in gaseous absorption bands including polarization. The method is a combination of doubling-adding and k-binning methods. We present an error estimation of this method by comparing with accurate line-by-line radiative transfer simulations. For the Motivated by several observations of the degree of linear polarization of skylight in the oxygen A (O(2)A) band that do not yet have a quantitative explanation, we analyze the influence of aerosol altitude, microphysics, and optical thickness on the degree of linear polarization of the zenith skylight in the spectral region of the O(2)A band, between 755 to 775 nm. It is shown that the degree of linear polarization inside the O(2)A band is particularly sensitive to aerosol altitude. The

  20. Observed correlations between aerosol and cloud properties in an Indian Ocean trade cumulus regime

    NASA Astrophysics Data System (ADS)

    Pistone, K.; Praveen, P. S.; Thomas, R. M.; Ramanathan, V.; Wilcox, E.; Bender, F. A.-M.

    2015-10-01

    There are many contributing factors which determine the micro- and macrophysical properties of clouds, including atmospheric structure, dominant meteorological conditions, and aerosol concentration, all of which may be coupled to one another. In the quest to determine aerosol effects on clouds, these potential relationships must be understood, as changes in atmospheric conditions due to aerosol may change the expected magnitude of indirect effects by altering cloud properties in unexpected ways. Here we describe several observed correlations between aerosol conditions and cloud and atmospheric properties in the Indian Ocean winter monsoon season. In the CARDEX (Cloud, Aerosol, Radiative forcing, Dynamics EXperiment) field campaign conducted in February and March 2012 in the northern Indian Ocean, continuous measurements of atmospheric precipitable water vapor and the liquid water path (LWP) of trade cumulus clouds were made, concurrent with measurements of water vapor flux, cloud and aerosol vertical profiles, meteorological data, and surface and total-column aerosol. Here we present evidence of a positive correlation between aerosol and cloud LWP which becomes clear after the data are filtered to control for the natural meteorological variability in the region. We then use the aircraft and ground observatory measurements to explore the mechanisms behind the observed aerosol-LWP correlation. We determine that increased boundary-layer humidity lowering the cloud base is responsible for the observed increase in cloud liquid water. Large-scale analysis indicates that high pollution cases originate with a highly-polluted boundary layer air mass approaching the observatory from a northwesterly direction. This polluted mass exhibits higher temperatures and humidity than the clean case, the former of which may be attributable to heating due to aerosol absorption of solar radiation over the subcontinent. While high temperature conditions dispersed along with the high-aerosol

  1. Synergy of Satellite-Surface Observations for Studying the Properties of Absorbing Aerosols in Asia

    NASA Technical Reports Server (NTRS)

    Tsay, Si-Chee

    2010-01-01

    , in major international research projects such as the Joint Aerosol Monsoon Experiment (JAM EX), a core element of the Asian Monsoon Years (AMY, 2008-2012). SMART-COMMIT deployments during 2008 AMY/JAMEX were conducted in northwestern China to characterize the properties of dust-laden aerosols and in the vicinity of Beijing for mega-city aerosols. In 2009, SMART-COMMIT also participated in the JAMEX/RAJO-MEGHA (Radiation, Aerosol Joint Observations-Monsoon Experiment in the Gangetic-Himalayan Area; Sanskrit for Dust-Cloud) to study the aerosol properties, solar absorption and the associated atmospheric warming, and the climatic impact of elevated aerosols during the pre-monsoon season in South Asia. We will show results from these field experiments, as well as discuss a new initiative of 7-SEAS (7 South East Asian Studies) to study the interaction of anthropogenic aerosols with regional meteorology, particularly with clouds.

  2. Optical properties of aerosol contaminated cloud derived from MODIS instrument

    NASA Astrophysics Data System (ADS)

    Mei, Linlu; Rozanov, Vladimir; Lelli, Luca; Vountas, Marco; Burrows, John P.

    2016-04-01

    The presence of absorbing aerosols above/within cloud can reduce the amount of up-welling radiation in visible (VIS) and short-wave infrared and darken the spectral reflectance when compared with a spectrum of a clean cloud observed by satellite instruments (Jethva et al., 2013). Cloud properties retrieval for aerosol contaminated cases is a great challenge. Even small additional injection of aerosol particles into clouds in the cleanest regions of Earth's atmosphere will cause significant effect on those clouds and on climate forcing (Koren et al., 2014; Rosenfeld et al., 2014) because the micro-physical cloud process are non-linear with respect to the aerosol loading. The current cloud products like Moderate Resolution Imaging Spectroradiometer (MODIS) ignoring the aerosol effect for the retrieval, which may cause significant error in the satellite-derived cloud properties. In this paper, a new cloud properties retrieval method, considering aerosol effect, based on the weighting-function (WF) method, is presented. The retrieval results shows that the WF retrieved cloud properties (e.g COT) agrees quite well with MODIS COT product for relative clear atmosphere (AOT ≤ 0.4) while there is a large difference for large aerosol loading. The MODIS COT product is underestimated for at least 2 - 3 times for AOT>0.4, and this underestimation increases with the increase of AOT.

  3. Aerosol physical properties in the stratosphere (APPS) radiometer design

    NASA Technical Reports Server (NTRS)

    Gray, C. R.; Woodin, E. A.; Anderson, T. J.; Magee, R. J.; Karthas, G. W.

    1977-01-01

    The measurement concepts and radiometer design developed to obtain earth-limb spectral radiance measurements for the Aerosol Physical Properties in the Stratosphere (APPS) measurement program are presented. The measurements made by a radiometer of this design can be inverted to yield vertical profiles of Rayleigh scatterers, ozone, nitrogen dioxide, aerosol extinction, and aerosol physical properties, including a Junge size-distribution parameter, and a real and imaginary index of refraction. The radiometer design provides the capacity for remote sensing of stratospheric constituents from space on platforms such as the space shuttle and satellites, and therefore provides for global measurements on a daily basis.

  4. Aerosol physical properties and their impact on climate change processes

    NASA Astrophysics Data System (ADS)

    Strzalkowska, Agata; Zielinski, Tymon; Petelski, Tomasz; Makuch, Przemyslaw; Pakszys, Paulina; Markuszewski, Piotr; Piskozub, Jacek; Drozdowska, Violetta; Gutowska, Dorota; Rozwadowska, Anna

    2013-04-01

    Characterizing aerosols involves the specification of not only their spatial and temporal distributions but their multi-component composition, particle size distribution and physical properties as well. Due to their light attenuation and scattering properties, aerosols influence radiance measured by satellite for ocean color remote sensing. Studies of marine aerosol production and transport are important for many earth sciences such as cloud physics, atmospheric optics, environmental pollution studies, and interaction between ocean and atmosphere. It was one of the reasons for the growth in the number of research programs dealing with marine aerosols. Sea salt aerosols are among the most abundant components of the atmospheric aerosol, and thus it exerts a strong influence on radiation, cloud formation, meteorology and chemistry of the marine atmosphere. An accurate understanding and description of these mechanisms is crucial to modeling climate and climate change. This work provides information on combined aerosol studies made with lidars and sun photometers onboard the ship and in different coastal areas. We concentrate on aerosol optical thickness and its variations with aerosol advections into the study area. We pay special attention to the problem of proper data collection and analyses techniques. We showed that in order to detect the dynamics of potential aerosol composition changes it is necessary to use data from different stations where measurements are made using the same techniques. The combination of such information with air mass back-trajectories and data collected at stations located on the route of air masses provides comprehensive picture of aerosol variations in the study area both vertically and horizontally. Acknowledgements: The support for this study was provided by the project Satellite Monitoring of the Baltic Sea Environment - SatBałtyk founded by European Union through European Regional Development Fund contract No. POIG 01

  5. Aerosol Optical Properties and Component Extinction from Measurements on the Ronald H. Brown During ACE-Asia

    NASA Astrophysics Data System (ADS)

    Quinn, P. K.; Bates, T. S.; Coffman, D.; Miller, T.; Anderson, J.

    2002-12-01

    Measurements of aerosol chemical, physical, and optical properties were made onboard the NOAA R/V Ronald H. Brown during the ACE-Asia Intensive Field Program to characterize Asian aerosol as it was transported across the Pacific Ocean. The ship traveled across the Pacific from Hawaii to Japan and into the East China Sea and the Sea of Japan. Based on trajectory analysis, the aerosol has been categorized as remote marine, volcanic from the Miyakejima volcano, polluted from Korea and Japan, polluted from Beijing, polluted mixed with dust during post frontal conditions, and polluted mixed with dust from Shanghai and Korea. Presented here, for these different categories, are aerosol optical properties (scattering and absorption coefficients, single scattering albedo (SSA), Angstrom Exponent, and aerosol optical depth), mass fractions of the major chemical components, and mass extinction efficiencies and extinction coefficients for individual aerosol components. Lowest scattering and absorption coefficients and highest single scattering albedos were measured in marine air masses encountered as the ship transited from Hawaii toward Japan (mean SSA = 0.97). Lowest SSA were measured in polluted air masses from Korea and Japan (mean SSA = 0.90). With dust mixed into the polluted air masses, SSA increased due to the high scattering levels associated with the dust (mean SSA ranged from 0.92 to 0.96 for different pollution/dust mixtures). These SSA are for the sub-10 micron aerosol at 55 percent RH. They were 1 to 4 percent lower for the sub-1 micron aerosol. Unique to the ACE Asia aerosol was the observation of significant absorption at 550 nm by supermicron aerosol. A correlation between supermicron elemental carbon concentrations and the ratio of absorption by sub-1 um aerosol to absorption by sub-10 um aerosol suggests that supermicron EC is responsible. As the mean concentration of supermicron EC increased from the marine to polluted to polluted with dust cases, the ratio

  6. Aerosol optical, microphysical and radiative properties at regional background insular sites in the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Sicard, Michaël; Barragan, Rubén; Dulac, François; Alados-Arboledas, Lucas; Mallet, Marc

    2016-09-01

    In the framework of the ChArMEx (the Chemistry-Aerosol Mediterranean Experiment; http://charmex.lsce.ipsl.fr/) program, the seasonal variability of the aerosol optical, microphysical and radiative properties derived from AERONET (Aerosol Robotic Network; http://aeronet.gsfc.nasa.gov/) is examined in two regional background insular sites in the western Mediterranean Basin: Ersa (Corsica Island, France) and Palma de Mallorca (Mallorca Island, Spain). A third site, Alborán (Alborán Island, Spain), with only a few months of data is considered for examining possible northeast-southwest (NE-SW) gradients of the aforementioned aerosol properties. The AERONET dataset is exclusively composed of level 2.0 inversion products available during the 5-year period 2011-2015. AERONET solar radiative fluxes are compared with ground- and satellite-based flux measurements. To the best of our knowledge this is the first time that AERONET fluxes are compared with measurements at the top of the atmosphere. Strong events (with an aerosol optical depth at 440 nm greater than 0.4) of long-range transport aerosols, one of the main drivers of the observed annual cycles and NE-SW gradients, are (1) mineral dust outbreaks predominant in spring and summer in the north and in summer in the south and (2) European pollution episodes predominant in autumn. A NE-SW gradient exists in the western Mediterranean Basin for the aerosol optical depth and especially its coarse-mode fraction, which all together produces a similar gradient for the aerosol direct radiative forcing. The aerosol fine mode is rather homogeneously distributed. Absorption properties are quite variable because of the many and different sources of anthropogenic particles in and around the western Mediterranean Basin: North African and European urban areas, the Iberian and Italian peninsulas, most forest fires and

  7. Influence of absorbing aerosols on the inference of solar surface radiation budget and cloud absorption

    SciTech Connect

    Li, Zhanqing

    1998-01-01

    This study addresses the impact of absorbing aerosols on the retrieval of the solar surface radiation budget (SSRB) and on the inference of cloud absorption using multiple global datasets. The data pertain to the radiation budgets at the top of the atmosphere (TOA), at the surface, and to precipitation and tropical biomass burning. Satellite-based SSRB data were derived from the Earth Radiation Budget Experiment and the International Satellite Cloud Climatology Program using different inversion algorithms. A manifestation of the aerosol effect emerges from a zonal comparison between satellite-based and surface-observed SSRB, which shows good agreement in most regions except over the tropical continents active in biomass burning. Another indication arises from the variation of the ratio of cloud radiative forcing at the TOA and at the surface, which was used in many recent studies addressing the cloud absorption problem. The author`s studies showed that the ratio is around unity under most circumstances except when there is heavy urban/industrial pollution or fires. These exceptions register discrepancy between observed and modeled SSRB. The discrepancy is found to increase with decreasing cloudiness, implying that it has more to do with the treatment of aerosols than clouds, although minor influences by other factors may also exist. The largest discrepancy is observed in the month of minimal cloud cover and maximal aerosol loading. The corresponding maximum monthly mean aerosol optical thickness is estimated to be around 1.0 by a parameterization developed in this study. After the effects of aerosols on SSRB are accounted for using biomass burning and precipitation data, disagreements no longer exist between the theory and observation with regard to the transfer of solar radiation. It should be pointed out that the tropical data employed in this study are limited to a small number of continental sites. 75 refs., 9 figs., 1 tab.

  8. The analysis of in situ and retrieved aerosol properties measured during three airborne field campaigns

    NASA Astrophysics Data System (ADS)

    Corr, Chelsea A.

    Aerosols can directly influence climate, visibility, and photochemistry by scattering and absorbing solar radiation. Aerosol chemical and physical properties determine how efficiently a particle scatters and/or absorbs incoming short-wave solar radiation. Because many types of aerosol can act as nuclei for cloud droplets (CCN) and a smaller population of airborne particles facilitate ice crystal formation (IN), aerosols can also alter cloud-radiation interactions which have subsequent impacts on climate. Thus aerosol properties determine the magnitude and sign of both the direct and indirect impacts of aerosols on radiation-dependent Earth System processes. This dissertation will fill some gaps in our understanding of the role of aerosol properties on aerosol absorption and cloud formation. Specifically, the impact of aerosol oxidation on aerosol spectral (350nm < lambda< 500nm) absorption was examined for two biomass burning plumes intercepted by the NASA DC-S aircraft during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission in Spring and Summer 2008. Spectral aerosol single scattering albedo (SSA) retrieved using actinic flux measured aboard the NASA DC-8 was used to calculate the aerosol absorption Angstrom exponents (AAE) for a 6-day-old plume on April 17 th and a 3-hour old plume on June 29th. Higher AAE values for the April 17th plume (6.78+/-0.38) indicate absorption by aerosol was enhanced in the ultraviolet relative to the visible portion of the short-wave spectrum in the older plume compared to the fresher plume (AAE= 3.34 0.11). These differences were largely attributed to the greater oxidation of the organic aerosol in the April 17th plume which can arise either from the aging of primary organic aerosol or the formation of spectrally-absorbing secondary organic aerosol. The validity of the actinic flux retrievals used above were also evaluated in this work by the comparison of SSA retrieved using

  9. Satellite remote sensing of aerosol and cloud properties over Eurasia

    NASA Astrophysics Data System (ADS)

    Sogacheva, Larisa; Kolmonen, Pekka; Saponaro, Giulia; Virtanen, Timo; Rodriguez, Edith; Sundström, Anu-Maija; Atlaskina, Ksenia; de Leeuw, Gerrit

    2015-04-01

    Satellite remote sensing provides the spatial distribution of aerosol and cloud properties over a wide area. In our studies large data sets are used for statistical studies on aerosol and cloud interaction in an area over Fennoscandia, the Baltic Sea and adjacent regions over the European mainland. This area spans several regimes with different influences on aerosol cloud interaction such as a the transition from relative clean air over Fennoscandia to more anthropogenically polluted air further south, and the influence maritime air over the Baltic and oceanic air advected from the North Atlantic. Anthropogenic pollution occurs in several parts of the study area, and in particular near densely populated areas and megacities, but also in industrialized areas and areas with dense traffic. The aerosol in such areas is quite different from that produced over the boreal forest and has different effects on air quality and climate. Studies have been made on the effects of aerosols on air quality and on the radiation balance in China. The aim of the study is to study the effect of these different regimes on aerosol-cloud interaction using a large aerosol and cloud data set retrieved with the (Advanced) Along Track Scanning Radiometer (A)ATSR Dual View algorithm (ADV) further developed at Finnish Meteorological Institute and aerosol and cloud data provided by MODIS. Retrieval algorithms for aerosol and clouds have been developed for the (A)ATSR, consisting of a series of instruments of which we use the second and third one: ATSR-2 which flew on the ERS-2 satellite (1995-2003) and AATSR which flew on the ENVISAT satellite (2002-2012) (both from the European Space Agency, ESA). The ADV algorithm provides aerosol data on a global scale with a default resolution of 10x10km2 (L2) and an aggregate product on 1x1 degree (L3). Optional, a 1x1 km2 retrieval products is available over smaller areas for specific studies. Since for the retrieval of AOD no prior knowledge is needed on

  10. An aerosol climatology for a rapidly growing arid region (southern Arizona): Major aerosol species and remotely sensed aerosol properties

    PubMed Central

    Sorooshian, Armin; Wonaschütz, Anna; Jarjour, Elias G.; Hashimoto, Bryce I.; Schichtel, Bret A.; Betterton, Eric A.

    2014-01-01

    This study reports a comprehensive characterization of atmospheric aerosol particle properties in relation to meteorological and back trajectory data in the southern Arizona region, which includes two of the fastest growing metropolitan areas in the United States (Phoenix and Tucson). Multiple data sets (MODIS, AERONET, OMI/TOMS, MISR, GOCART, ground-based aerosol measurements) are used to examine monthly trends in aerosol composition, aerosol optical depth (AOD), and aerosol size. Fine soil, sulfate, and organics dominate PM2.5 mass in the region. Dust strongly influences the region between March and July owing to the dry and hot meteorological conditions and back trajectory patterns. Because monsoon precipitation begins typically in July, dust levels decrease, while AOD, sulfate, and organic aerosol reach their maximum levels because of summertime photochemistry and monsoon moisture. Evidence points to biogenic volatile organic compounds being a significant source of secondary organic aerosol in this region. Biomass burning also is shown to be a major contributor to the carbonaceous aerosol budget in the region, leading to enhanced organic and elemental carbon levels aloft at a sky-island site north of Tucson (Mt. Lemmon). Phoenix exhibits different monthly trends for aerosol components in comparison with the other sites owing to the strong influence of fossil carbon and anthropogenic dust. Trend analyses between 1988 and 2009 indicate that the strongest statistically significant trends are reductions in sulfate, elemental carbon, and organic carbon, and increases in fine soil during the spring (March–May) at select sites. These results can be explained by population growth, land-use changes, and improved source controls. PMID:24707452

  11. Influences of relative humidity and particle chemical composition on aerosol scattering properties during the 2006 PRD campaign

    NASA Astrophysics Data System (ADS)

    Liu, Xingang; Cheng, Yafang; Zhang, Yuanhang; Jung, Jinsang; Sugimoto, Nobuo; Chang, Shih-Yu; Kim, Young J.; Fan, Shaojia; Zeng, Limin

    In situ measurements of the physical, chemical, and optical properties of aerosols were carried out in Guangzhou city, China, from 1 to 31 July 2006 during the Pearl River Delta (PRD) Campaign. The light extinction coefficient of the ambient atmosphere, the aerosol scattering coefficient under dry conditions, the aerosol absorption coefficient under ambient conditions, NO 2 concentration, and relative humidity (RH) were measured by transmissionmeter, an integrating nephelometer, a multi-angle absorption photometer (MAAP), a NO X analyzer, and an automatic meteorological station, respectively. Meanwhile, the molecular scattering coefficient was calculated by the Rayleigh scattering function using the US Standard Atmosphere. A method to calculate the aerosol hygroscopic growth factor f(RH), defined as the ratio of the aerosol scattering coefficient under a wet condition to that under a dry condition (40% RH), is proposed based on these optical parameters. The mean and standard deviation aerosol hygroscopic growth factors at 80% RH ( f(RH)=80%) in Ganzhou were 2.04±0.28, 2.29±0.28, and 2.68±0.59 for urban aerosols, mixed aerosols, and marine aerosols, respectively, with the air mass classification being based on the air mass source region. The relationship between f(RH) and RH is fitted by empirical equations and the fitting parameters are calculated. The relationships between f(RH)=80% and total carbon mass fraction (TCF) in PM 2.5, the water-soluble mass fraction (WSF) in PM 10, and the sea-salt aerosol mass fraction (SSF) in PM 10 reveal that the hygroscopic properties of the observed aerosol have a good positive correlation with the WSF and SSF, but have a negative correlation with the TCF.

  12. Optical constants of ammonium sulfate in the infrared. [stratospheric aerosol refractive and absorption indices

    NASA Technical Reports Server (NTRS)

    Downing, H. D.; Pinkley, L. W.; Sethna, P. P.; Williams, D.

    1977-01-01

    The infrared spectral reflectance at near normal incidence has been measured for 3.2 M, 2.4 M, and 1.6 M solutions of ammonium sulfate, an aerosol abundant in the stratosphere and also present in the troposphere. Kramers-Kronig analysis was used to determine values of the refractive and absorption indices from the measured spectral reflectance. A synthetic spectrum of crystalline ammonium sulfate was obtained by extrapolation of the absorption index obtained for the solution to the absorber number densities of the NH4 and SO4 ions characteristic of the crystal.

  13. Aerosol Physical and Chemical Properties Before and After the Manaus Plume in the GoAmazon2014 Experiment

    NASA Astrophysics Data System (ADS)

    Artaxo, P.; Barbosa, H. M.; Ferreira De Brito, J.; Wurm, F.; Holanda, B. A.; Carbone, S.; Arana, A.; Cirino, G. G.; Souza, R. A. F. D.; Rizzo, L. V.; Martin, S. T.; Andreae, M. O.; Holben, B. N.; Schafer, J.

    2014-12-01

    As part of the GoAmazon2014 experiment, several aerosol and trace gas monitoring stations are being operated for at least one year before and after the Manaus plume. Three sites are being operated in pristine conditions, with atmospheric properties under natural biogenic conditions. These three sites called T0 are: ATTO (Amazon Tall Tower Observatory), ZF2 ecological research site and a third site called EMBRAPA. After the air masses are exposed to the Manaus plume, one site (called T2) is being operated right on the opposite side of the Negro River under the direct influence of the Manaus plume at 5 Km downwind of Manaus. Finally, at about 150 Km downwind of Manaus is the T3 Manacapuru site. Aerosol chemical composition is being analyzed using filters for fine (PM2.5) and coarse mode aerosol as well as three Aerodyne ACSM (Aerosol Chemical Speciation Monitors) instruments. Aerosol absorption is being studied with several aethalometers and MAAP (Multi Angle Absorption Photometers). Aerosol light scattering are being measured at several wavelengths using nephelometers. Aerosol size distribution is determined using scanning mobility particle sizers. The aerosol column is measures using AERONET sunphotometers before and after the Manaus plume, as well as several Lidar systems. The three sites before the Manaus plume show remarkable similar variability in aerosol concentrations and optical properties. This pattern is very different at the T2 site, with large aerosol concentrations enhancing aerosol absorption and scattering significantly. The aerosol is very oxidized before being exposed to the Manaus plume, and this pattern changes significantly for T2 and T3 sites, with a much higher presence of less oxidized aerosol. Typical ozone concentrations at mid-day before Manaus plume is a low 10-12 ppb, value that changes to 50-70 ppb for air masses suffering the influence of Manaus plume. A detailed comparison of aerosol characteristics and composition for the several

  14. Airborne Lidar Measurements of Aerosol Optical Properties During SAFARI-2000

    NASA Technical Reports Server (NTRS)

    McGill, M. J.; Hlavka, D. L.; Hart, W. D.; Welton, E. J.; Campbell, J. R.; Starr, David OC. (Technical Monitor)

    2002-01-01

    The Cloud Physics Lidar (CPL) operated onboard the NASA ER-2 high altitude aircraft during the SAFARI-2000 field campaign. The CPL provided high spatial resolution measurements of aerosol optical properties at both 1064 nm and 532 nm. We present here results of planetary boundary layer (PBL) aerosol optical depth analysis and profiles of aerosol extinction. Variation of optical depth and extinction are examined as a function of regional location. The wide-scale aerosol mapping obtained by the CPL is a unique data set that will aid in future studies of aerosol transport. Comparisons between the airborne CPL and ground-based MicroPulse Lidar Network (MPL-Net) sites are shown to have good agreement.

  15. Retrieval of Aerosol Microphysical Properties from MFRSR Observations

    SciTech Connect

    Kassianov, Evgueni I; Barnard, James C; Ackerman, Thomas P

    2006-05-01

    Aerosols can have significant impact on the radiative and heat balance of the Earth-atmosphere system by absorbing and scattering solar radiation (direct aerosol effect) and altering cloud optical properties and suppressing precipitation (indirect aerosol effect). However, both the sign and magnitude of the aerosol impact has proven difficult to determine due to incomplete knowledge of aerosol properties and their strong temporal and spatial variations. Reduction of these uncertainties requires an accurate global inventory of aerosol microphysical properties, such as size distribution and the refractive index. Multi-filter Rotating Shadowband Radiometers (MFRSRs) are widely deployed over the world (e.g., the surface radiation budget network). These radiometers provide measurements of the direct and the diffuse solar irradiances at six wavelengths (0.415, 0.5, 0.615, 0.673, 0.870 and 0.94 ). Currently, the direct irradiance observations are used to derive routinely spectral values of the aerosol optical depth only. We propose a simple retrieval technique that significantly extends the capability of the MFRSR to study atmospheric aerosols. In our retrieval, we assume the shape of aerosol size distribution (e.g., combination of three lognormal distributions) and the value of the real refractive index. The technique consists of three steps that compose an iterative scheme. The first step obtains the aerosol size distribution from the spectral measurements of the direct irradiance (for a given complex refractive index). To reduce the effect of ozone and water vapor contamination, we use wavelengths where ozone and water vapor weakly affect the direct irradiance (0.415 mu and 0.870 mu). The second step determines the effective value of the imaginary refractive index from the diffuse irradiance (for the aerosol size distribution determined during the first step). To reduce the effect of the surface albedo on the retrievals, we select a wavelength where the surface albedo

  16. Observed correlations between aerosol and cloud properties in an Indian Ocean trade cumulus regime

    NASA Astrophysics Data System (ADS)

    Pistone, Kristina; Praveen, Puppala S.; Thomas, Rick M.; Ramanathan, Veerabhadran; Wilcox, Eric M.; Bender, Frida A.-M.

    2016-04-01

    There are many contributing factors which determine the micro- and macrophysical properties of clouds, including atmospheric vertical structure, dominant meteorological conditions, and aerosol concentration, all of which may be coupled to one another. In the quest to determine aerosol effects on clouds, these potential relationships must be understood. Here we describe several observed correlations between aerosol conditions and cloud and atmospheric properties in the Indian Ocean winter monsoon season.In the CARDEX (Cloud, Aerosol, Radiative forcing, Dynamics EXperiment) field campaign conducted in February and March 2012 in the northern Indian Ocean, continuous measurements were made of atmospheric precipitable water vapor (PWV) and the liquid water path (LWP) of trade cumulus clouds, concurrent with measurements of water vapor flux, cloud and aerosol vertical profiles, meteorological data, and surface and total-column aerosol from instrumentation at a ground observatory and on small unmanned aircraft. We present observations which indicate a positive correlation between aerosol and cloud LWP only when considering cases with low atmospheric water vapor (PWV < 40 kg m-2), a criterion which acts to filter the data to control for the natural meteorological variability in the region.We then use the aircraft and ground-based measurements to explore possible mechanisms behind this observed aerosol-LWP correlation. The increase in cloud liquid water is found to coincide with a lowering of the cloud base, which is itself attributable to increased boundary layer humidity in polluted conditions. High pollution is found to correlate with both higher temperatures and higher humidity measured throughout the boundary layer. A large-scale analysis, using satellite observations and meteorological reanalysis, corroborates these covariations: high-pollution cases are shown to originate as a highly polluted boundary layer air mass approaching the observatory from a northwesterly

  17. Optical, physical, and chemical properties of springtime aerosol over Barrow Alaska in 2008

    SciTech Connect

    Shantz, Nicole C.; Gultepe, Ismail; Andrews, Elisabeth; Earle, Michael; MacDonald, A. M.; Liu, Peter S.K.; Leaitch, W. R.

    2014-03-06

    Airborne observations from four flights during the 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC) are used to examine some cloud-free optical, physical, and chemical properties of aerosol particles in the springtime Arctic troposphere. The number concentrations of particles larger than 0.12 μm (Na>120), important for light extinction and cloud droplet formation, ranged from 15 to 2260 cm-3, with the higher Na>120 cases dominated by measurements from two flights of long-range transported biomass burning (BB) aerosols. The two other flights examined here document a relatively clean aerosol and an Arctic Haze aerosol impacted by larger particles largely composed of dust. For observations from the cleaner case and the BB cases, the particle light scattering coefficients at low relative humidity (RH<20%) increased nonlinearly with increasing Na>120, driven mostly by an increase in mean sizes of particles with increasing Na>120 (BB cases). For those three cases, particle light absorption coefficients also increased nonlinearly with increasing Na>120 and linearly with increasing submicron particle volume concentration. In addition to black carbon, brown carbon was estimated to have increased light absorption coefficients by 27% (450 nm wavelength) and 14% (550 nm) in the BB cases. For the case with strong dust influence, the absorption relative to submicron particle volume was small compared with the other cases. There was a slight gradient of Passive Cavity Aerosol Spectrometer Probe (PCASP) mean volume diameter (MVD) towards smaller sizes with increasing height, which suggests more scavenging of the more elevated particles, consistent with a typically longer lifetime of particles higher in the atmosphere. However, in approximately 10% of the cases, the MVD increased (>0.4 μm) with increasing altitude, suggesting transport of larger fine particle mass (possibly coarse particle mass) at high levels over the Arctic. This may be because of transport of

  18. Differences in aerosol absorption Ångström exponents between correction algorithms for particle soot absorption photometer measured on South African Highveld

    NASA Astrophysics Data System (ADS)

    Backman, J.; Virkkula, A.; Vakkari, V.; Beukes, J. P.; Van Zyl, P.; Josipovic, M.; Piketh, S.; Tiitta, P.; Chiloane, K.; Petäjä, T.; Kulmala, M.; Laakso, L.

    2014-09-01

    Absorption Ångstrom exponents (AAE) calculated from filter-based absorption measurements are often used to give information on the origin of the ambient aerosol, for example to distinguish between urban pollution and biomass burning aerosol. Filter-based absorption measurements are a widely used method and are commonly used at aerosol monitoring stations globally. Several correction algorithms are used to account for the artifacts associated with filter-based absorption techniques. These algorithms are of profound importance when determining the absolute amount of absorption by the aerosol. However, this study shows that there are significant differences between the AAEs calculated from these corrections. The study also shows that the difference between AAEs calculated using different corrections can lead to conflicting conclusions on the type of aerosol for the same data set. In this work the AAEs were calculated from data measured with a three-wavelength Particle Soot Absorption Photometer (PSAP) at Elandsfontein on deployed on the South African Highveld for 23 months. The sample air of the PSAP was diluted to prolong filter change intervals. The dilution-corrected PSAP showed a good agreement with a non-diluted MAAP. Thus, the study also shows that the applicability of the PSAP can be extended to remote sites are not often visited or suffer from high levels of pollution.

  19. Aerosol properties over south india during different seasons

    NASA Astrophysics Data System (ADS)

    Sivaprasad, P.; Babu, C. A.; Jayakrishnan, P. R.

    Aerosols play an important role in the radiation balance and cloud properties, thereby affect the entire climatology of the earth-atmosphere system. Besides natural sources like dust, seasalt and natural sulphates, anthropogenic activities also inject aerosols like soot and industrial sulphates. Of these sea-salt and sulphates scatter the solar radiation. Soot is an absorbing aerosol while soil dust and organic matters are partly absorbing aerosols. Wind and rainfall are major factors affecting the transportation and deposition of the aerosols. India is a country blessed with plenty of monsoon rains. Winter (December to February), summer (March to May), monsoon (June to September) and post monsoon (October to November) are the four seasons over the region. Aerosol properties vary according to the season. Natural aerosols blown from the deserts have a major role in the aerosol optical depth over India. Of this, dust from Arabian desert that is carried by the winds are most important. The aerosol optical depth of south India is entirely different from that of north India. Maximum aerosol concentration is found over Gangetic plane in most of the seasons, whereas entire south India shows less aerosol optical depth. In the present study the aerosol properties of south India is analysed in general. Particular analysis is carried out for the four regions in the east and west coasts around Chennai, Kolkotha, Mumbai and Cochin. Chennai and Kolkotha are situated in the east coast whereas Cochin and Mumbai are in the west coast. These are industrial cities in India. Chennai region does not get monsoon rainfall since it is situated in the leeward side of Western ghats. But in the post monsoon season Chennai gets good amount of rainfall. Other three regions get good amount of rainfall during monsoon season. The study uses Terra MODIS, TOMS, NCEP/NCAR and TRMM data. Aerosol properties are analysed using Terra MODIS and Nimbus TOMS data. The variations of the aerosol optical

  20. Airborne Sunphotometer Studies of Aerosol Properties and Effects, Including Closure Among Satellite, Suborbital Remote, and In situ Measurements

    NASA Technical Reports Server (NTRS)

    Russlee, Philip B.; Schmid, B.; Redemann, J.; Livingston, J. M.; Bergstrom, R. W.; Ramirez, S. A.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    Airborne sunphotometry has been used to measure aerosols from North America, Europe, and Africa in coordination with satellite and in situ measurements in TARFOX (1996), ACE-2 (1997), PRIDE (2000), and SAFARI 2000. Similar coordinated measurements of Asian aerosols are being conducted this spring in ACE-Asia and are planned for North American aerosols this summer in CLAMS. This paper summarizes the approaches used, key results, and implications for aerosol properties and effects, such as single scattering albedo and regional radiative forcing. The approaches exploit the three-dimensional mobility of airborne sunphotometry to access satellite scenes over diverse surfaces (including open ocean with and without sunglint) and to match exactly the atmospheric layers sampled by airborne in situ measurements and other radiometers. These measurements permit tests of the consistency, or closure, among such diverse measurements as aerosol size-resolved chemical composition; number or mass concentration; light extinction, absorption, and scattering (total, hemispheric back and 180 deg.); and radiative fluxes. In this way the airborne sunphotometer measurements provide a key link between satellite and in situ measurements that helps to understand any discrepancies that are found. These comparisons have led to several characteristic results. Typically these include: (1) Better agreement among different types of remote measurements than between remote and in situ measurements. (2) More extinction derived from transmission measurements than from in situ measurements. (3) Larger aerosol absorption inferred from flux radiometry than from in situ measurements. Aerosol intensive properties derived from these closure studies have been combined with satellite-retrieved fields of optical depth to produce fields of regional radiative forcing. We show results for the North Atlantic derived from AVHRR optical depths and aerosol intensive properties from TARFOX and ACE-2. Companion papers

  1. Development of 2-D-MAX-DOAS and retrievals of trace gases and aerosols optical properties

    NASA Astrophysics Data System (ADS)

    Ortega, Ivan

    Air pollution is a major problem worldwide that adversely a_ects human health, impacts ecosystems and climate. In the atmosphere, there are hundreds of important compounds participating in complex atmospheric reactions linked to air quality and climate. Aerosols are relevant because they modify the radiation balance, a_ect clouds, and thus Earth albedo. The amount of aerosol is often characterized by the vertical integral through the entire height of the atmosphere of the logarithm fraction of incident light that is extinguished called Aerosol Optical Depth (AOD). The AOD at 550 nm (AOD550) over land is 0.19 (multi annual global mean), and that over oceans is 0.13. About 43 % of the Earth surface shows AOD550 smaller than 0.1. There is a need for measurement techniques that are optimized to measure aerosol optical properties under low AOD conditions, sample spatial scales that resemble satellite ground-pixels and atmospheric models, and help integrate remote sensing and in-situ observations to obtain optical closure on the effects of aerosols and trace gases in our changing environment. In this work, I present the recent development of the University of Colorado two dimensional (2-D) Multi-AXis Differential Optical Absorption Spectroscopy (2-D-MAX-DOAS) instrument to measure the azimuth and altitude distribution of trace gases and aerosol optical properties simultaneously with a single instrument. The instrument measures solar scattered light from any direction in the sky, including direct sun light in the hyperspectral domain. In Chapter 2, I describe the capabilities of 2-D measurements in the context of retrievals of azimuth distributions of nitrogen dioxide (NO2), formaldehyde (HCHO), and glyoxal (CHOCHO), which are precursors for tropospheric O3 and aerosols. The measurements were carried out during the Multi-Axis DOAS Comparison campaign for Aerosols and Trace gases (MAD-CAT) campaign in Mainz, Germany and show the ability to bridge spatial scales to

  2. Particle Property Data Quality Flags for the MISR Aerosol Product

    NASA Astrophysics Data System (ADS)

    Gaitley, B. J.; Kahn, R. A.; Garay, M. J.

    2013-12-01

    The MISR instrument aboard the NASA Earth Observing System's Terra satellite has the unique capability to retrieve aerosol properties under favorable conditions. General aerosol type retrieval quality guidelines are provided in the MISR Data Quality Statement and related publications. The retrieved value of aerosol type is more sensitive to scene conditions than aerosol optical depth, and more difficult to validate, as there is very little coincident aerosol type validation data. Here we report on the steps we are taking to provide an aerosol-type data quality flag, to be provided with each individual retrieval result. Due to the lack of validation data for comparison, our main approach is to evaluate the self-consistency of aerosol type retrieval values for regions where particular aerosol types are known to dominate. Some factors affecting aerosol type retrieval quality that can be assessed pre-retrieval are the number of MISR cameras available, the range of scattering angles viewed, and surface conditions such as shallow water or seasonal coastal runoff. Factors that must be assessed post-retrieval include values of retrieved aerosol optical depth and the number and type of mixtures successfully passing the MISR algorithm acceptance criteria. Regional monthly plots with MISR measurements binned at 0.5 degree resolution and color-coded stratification of one or more parameters are the main tools for identifying locations and times where different aerosol types are retrieved. The statistics of individual MISR values such as mid-visible AOD, number and type of mixtures passing, number of cameras used, the range and maximum scattering angles, are studied as joint distributions on a region-by-region basis. From these, a synthesis of the self-consistency and agreement with expectation is made, effectively indicating the quality of the aerosol type constrains to the extent possible, and thresholds for assigning quality flags are assessed. Multiple-month summaries

  3. Dependence of Aerosol Light Absorption and Single-Scattering Albedo On Ambient Relative Humidity for Sulfate Aerosols with Black Carbon Cores

    NASA Technical Reports Server (NTRS)

    Redemann, Jens; Russell, Philip B.; Hamill, Patrick

    2001-01-01

    Atmospheric aerosols frequently contain hygroscopic sulfate species and black carbon (soot) inclusions. In this paper we report results of a modeling study to determine the change in aerosol absorption due to increases in ambient relative humidity (RH), for three common sulfate species, assuming that the soot mass fraction is present as a single concentric core within each particle. Because of the lack of detailed knowledge about various input parameters to models describing internally mixed aerosol particle optics, we focus on results that were aimed at determining the maximum effect that particle humidification may have on aerosol light absorption. In the wavelength range from 450 to 750 nm, maximum absorption humidification factors (ratio of wet to 'dry=30% RH' absorption) for single aerosol particles are found to be as large as 1.75 when the RH changes from 30 to 99.5%. Upon lesser humidification from 30 to 80% RH, absorption humidification for single particles is only as much as 1.2, even for the most favorable combination of initial ('dry') soot mass fraction and particle size. Integrated over monomodal lognormal particle size distributions, maximum absorption humidification factors range between 1.07 and 1.15 for humidification from 30 to 80% and between 1.1 and 1.35 for humidification from 30 to 95% RH for all species considered. The largest humidification factors at a wavelength of 450 nm are obtained for 'dry' particle size distributions that peak at a radius of 0.05 microns, while the absorption humidification factors at 700 nm are largest for 'dry' size distributions that are dominated by particles in the radius range of 0.06 to 0.08 microns. Single-scattering albedo estimates at ambient conditions are often based on absorption measurements at low RH (approx. 30%) and the assumption that aerosol absorption does not change upon humidification (i.e., absorption humidification equal to unity). Our modeling study suggests that this assumption alone can

  4. Aircraft Observations of Marine Aerosol Properties in the Presence of Boundary Layer Rolls

    NASA Astrophysics Data System (ADS)

    Kapustin, V.; Clarke, A.; Howell, S.; Conley, S.; Faloona, I.; Brekhovskikh, V.; McNaughton, C.

    2008-12-01

    The Hawaii Group for Environmental Aerosol Research deployed a wide range of airborne aerosol instrumentation as part of MILAGRO/INTEX (2006) and PASE (2007) experiments. These were designed to provide rapid information on aerosol composition, state of mixing (internal or external), spectral optical properties (scattering and absorption), the humidity dependence of light scattering - f(RH). The measurements revealed frequently observed presence of numerous periodic structures related both to horizontal convective rolls (HCRs) and Kelvin-Helmholtz instability (KHI). HCRs, commonly formed when some vertical wind shear is present, are significant to the vertical transport of momentum, heat, moisture, and air pollutant including aerosols within the boundary layer. KHIs, occurred in areas of enhanced velocity shear and/or a local minimum of static stability, contribute strongly to the dissipation of large-scale motions into turbulence. This presentation focused on the direct in-situ marine aerosol properties in the presence of BL rolls by providing evidence that the observed variations are caused by rolls. We also studied whether the presence of rolls leads to the enhancement of aerosol fluxes. We have investigated roll structures in diverse MBL settings and have demonstrated that these can play an active role in the redistribution of aerosol, gas and water vapor in the MBL. Depending upon the thermodynamic profiles and the roll size, altitude, temporal duration these rolls can have a marked effect on the exchange of air masses between the buffer layer, the surface mixed layer and the free troposphere. This will lead to changes in the horizontal extinction in these layers relative to regions not influenced by the rolls. Hence, the evolution of aerosol optical properties in the near-surface mixed layer will be affected by rolls and the conditions that stimulate them. These can occur with or without associated cloud features. Some ongoing studies include the following

  5. Retrieval of aerosol optical and micro-physical properties with 2D-MAX-DOAS

    NASA Astrophysics Data System (ADS)

    Ortega, Ivan; Coburn, Sean; Hostetler, Chris; Ferrare, Rich; Hair, Johnathan; Kassianov, Evgueni; Barnard, James; Berg, Larry; Schmid, Beat; Tomlinson, Jason; Hodges, Gary; Lantz, Kathy; Wagner, Thomas; Volkamer, Rainer

    2015-04-01

    Recent retrievals of 2 dimensional (2D) Multi-AXis Differential Optical Absorption Spectroscopy (2D-MAX-DOAS) have highlighted its importance in order to infer diurnal horizontal in-homogeneities around the measurement site. In this work, we expand the capabilities of 2D measurements in order to estimate simultaneously aerosol optical and micro-physical properties. Specifically, we present a retrieval method to obtain: (1) aerosol optical thickness (AOT) in the boundary layer (BL) and free troposphere (FT) and (2) the effective complex refractive index and the effective radius of the aerosol column size distribution. The retrieval method to obtain AOT is based on an iterative comparison of measured normalized radiances, oxygen collision pair (O4), and absolute Raman Scattering Probability (RSP) with the forward model calculations derived with the radiative transfer model McArtim based on defined aerosol extinction profiles. Once the aerosol load is determined we use multiple scattering phase functions and single scattering albedo (SSA) obtained with Mie calculations which then constrain the RTM to forward model solar almucantar normalized radiances. The simulated almucantar normalized radiances are then compared to the measured normalized radiances. The best-fit, determined by minimizing the root mean square, retrieves the complex refractive index, and effective radius. We apply the retrieval approach described above to measurements carried out during the 2012 intensive operation period of the Two Column Aerosol Project (TCAP) held on Cape Cod, MA, USA. Results are presented for two ideal case studies with both large and small aerosol loading and similar air mass outflow from the northeast coast of the US over the West Atlantic Ocean. The aerosol optical properties are compared with several independent instruments, including the NASA Langley airborne High Spectral Resolution Lidar (HSRL-2) for highly resolved extinction profiles during the overpasses, and with the

  6. Investigation of the seasonal variations of aerosol physicochemical properties and their impact on cloud condensation nuclei number concentration

    NASA Astrophysics Data System (ADS)

    Logan, Timothy S.

    Aerosols are among the most complex yet widely studied components of the atmosphere not only due to the seasonal variability of their physical and chemical properties but also their effects on climate change. The three main aerosol types that are known to affect the physics and chemistry of the atmosphere are: mineral dust, anthropogenic pollution, and biomass burning aerosols. In order to understand how these aerosols affect the atmosphere, this dissertation addresses the following three scientific questions through a combination of surface and satellite observations: SQ1: What are the seasonal and regional variations of aerosol physico-chemical properties at four selected Asian sites? SQ2: How do these aerosol properties change during transpacific and intra-continental long range transport? SQ3: What are the impacts of aerosol properties on marine boundary layer cloud condensation nuclei number concentration? This dissertation uses an innovative approach to classify aerosol properties by region and season to address SQ1. This is useful because this method provides an additional dimension when investigating the physico-chemical properties of aerosols by linking a regional and seasonal dependence to both the aerosol direct and indirect effects. This method involves isolating the aerosol physico-chemical properties into four separate regions using AERONET retrieved Angstrom exponent (AEAOD) and single scattering co-albedo (o oabs) to denote aerosol size and absorptive properties. The aerosols events are then clustered by season. The method is first applied to four AERONET sites representing single mode aerosol dominant regions: weakly absorbing pollution (NASA Goddard), strongly absorbing pollution (Mexico City), mineral dust (Solar Village), and biomass burning smoke (Alta Floresta). The method is then applied to four Asian sites that represent complicated aerosol components. There are strong regional and seasonal influences of the four aerosol types over the

  7. Estimation of aerosol optical properties from all-sky imagers

    NASA Astrophysics Data System (ADS)

    Kazantzidis, Andreas; Tzoumanikas, Panagiotis; Salamalikis, Vasilios; Wilbert, Stefan; Prahl, Christoph

    2015-04-01

    Aerosols are one of the most important constituents in the atmosphere that affect the incoming solar radiation, either directly through absorbing and scattering processes or indirectly by changing the optical properties and lifetime of clouds. Under clear skies, aerosols become the dominant factor that affect the intensity of solar irradiance reaching the ground. It has been shown that the variability in direct normal irradiance (DNI) due to aerosols is more important than the one induced in global horizontal irradiance (GHI), while the uncertainty in its calculation is dominated by uncertainties in the aerosol optical properties. In recent years, all-sky imagers are used for the detection of cloud coverage, type and velocity in a bouquet of applications including solar irradiance resource and forecasting. However, information about the optical properties of aerosols could be derived with the same instrumentation. In this study, the aerosol optical properties are estimated with the synergetic use of all-sky images, complementary data from the Aerosol Robotic Network (AERONET) and calculations from a radiative transfer model. The area of interest is Plataforma Solar de Almería (PSA), Tabernas, Spain and data from a 5 month period are analyzed. The proposed methodology includes look-up-tables (LUTs) of diffuse sky radiance of Red (R), Green (G) and Blue (B) channels at several zenith and azimuth angles and for different atmospheric conditions (Angström α and β, single scattering albedo, precipitable water, solar zenith angle). Based on the LUTS, results from the CIMEL photometer at PSA were used to estimate the RGB radiances for the actual conditions at this site. The methodology is accompanied by a detailed evaluation of its robustness, the development and evaluation of the inversion algorithm (derive aerosol optical properties from RGB image values) and a sensitivity analysis about how the pre-mentioned atmospheric parameters affect the results.

  8. Improving satellite-retrieved aerosol microphysical properties using GOCART data

    NASA Astrophysics Data System (ADS)

    Li, S.; Kahn, R.; Chin, M.; Garay, M. J.; Liu, Y.

    2015-03-01

    The Multi-angle Imaging SpectroRadiometer (MISR) aboard the NASA Earth Observing System's Terra satellite can provide more reliable aerosol optical depth (AOD) and better constraints on particle size (Ångström exponent, or ANG), sphericity, and single-scattering albedo (SSA) than many other satellite instruments. However, many aerosol mixtures pass the algorithm acceptance criteria, yielding a poor constraint, when the particle-type information in the MISR radiances is low, typically at low AOD. We investigate adding value to the MISR aerosol product under these conditions by filtering the list of MISR-retrieved mixtures based on agreement between the mixture ANG and absorbing AOD (AAOD) values, and simulated aerosol properties from the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model. MISR-GOCART ANG difference and AAOD ratio thresholds for applying GOCART constraints were determined based on coincident AOD, ANG, and AAOD measurements from the AErosol RObotic NETwork (AERONET). The results were validated by comparing the adjusted MISR aerosol optical properties over the contiguous USA between 2006 and 2009 with additional AERONET data. The correlation coefficient (r) between the adjusted MISR ANG derived from this study and AERONET improves to 0.45, compared to 0.29 for the MISR Version 22 standard product. The ratio of the adjusted MISR AAOD to AERONET increases to 0.74, compared to 0.5 for the MISR operational retrieval. These improvements occur primarily when AOD < 0.2 for ANG and AOD < 0.5 for AAOD. Spatial and temporal differences among the aerosol optical properties of MISR V22, GOCART, and the adjusted MISR are traced to (1) GOCART underestimation of AOD and ANG in polluted regions; (2) aerosol mixtures lacking in the MISR Version 22 algorithm climatology; (3) low MISR sensitivity to particle type under some conditions; and (4) parameters and thresholds used in our method.

  9. Aerosol-halogen interaction: Change of physico-chemical properties of SOA by naturally released halogen species

    NASA Astrophysics Data System (ADS)

    Ofner, J.; Balzer, N.; Buxmann, J.; Grothe, H.; Krüger, H.; Platt, U.; Schmitt-Kopplin, P.; Zetzsch, C.

    2011-12-01

    Reactive halogen species are released by various sources like photo-activated sea-salt aerosol or salt pans and salt lakes. These heterogeneous release mechanisms have been overlooked so far, although their potential of interaction with organic aerosols like Secondary Organic Aerosol (SOA), Biomass Burning Organic Aerosol (BBOA) or Atmospheric Humic LIke Substances (HULIS) is completely unknown. Such reactions can constitute sources of gaseous organo-halogen compounds or halogenated organic particles in the atmospheric boundary layer. To study the interaction of organic aerosols with reactive halogen species (RHS), SOA was produced from α-pinene, catechol and guaiacol using an aerosol smog-chamber. The model SOAs were characterized in detail using a variety of physico-chemical methods (Ofner et al., 2011). Those aerosols were exposed to molecular halogens in the presence of UV/VIS irradiation and to halogens, released from simulated natural halogen sources like salt pans, in order to study the complex aerosol-halogen interaction. The heterogeneous reaction of RHS with those model aerosols leads to different gaseous species like CO2, CO and small reactive/toxic molecules like phosgene (COCl2). Hydrogen containing groups on the aerosol particles are destroyed to form HCl or HBr, and a significant formation of C-Br bonds could be verified in the particle phase. Carbonyl containing functional groups of the aerosol are strongly affected by the halogenation process. While changes of functional groups and gaseous species were visible using FTIR spectroscopy, optical properties were studied using Diffuse Reflectance UV/VIS spectroscopy. Overall, the optical properties of the processed organic aerosols are significantly changed. While chlorine causes a "bleaching" of the aerosol particles, bromine shifts the maximum of UV/VIS absorption to the red end of the UV/VIS spectrum. Further physico-chemical changes were recognized according to the aerosol size-distributions or the

  10. Relationship between Oxidation Level and Optical Properties of Secondary Organic Aerosol

    NASA Astrophysics Data System (ADS)

    Lambe, A. T.; Cappa, C. D.; Massoli, P.; Onasch, T. B.; Forestieri, S.; Martin, A. T.; Cummings, M. J.; Croasdale, D. R.; Brune, W. H.; Worsnop, D. R.; Davidovits, P.

    2013-12-01

    Brown carbon (BrC), which may include secondary organic aerosol (SOA), can be a significant climate-forcing agent via its optical absorption properties. However, the overall contribution of SOA to BrC remains poorly understood. Here, correlations between oxidation level and optical properties of SOA are examined. SOA was generated in a flow reactor in the absence of NOx by OH oxidation of gas-phase precursors used as surrogates for anthropogenic (naphthalene, tricyclo-[5.2.1.02,6]decane), biomass burning (guaiacol), and biogenic (α-pinene) emissions. SOA chemical composition was characterized with a time-of-flight aerosol mass spectrometer. SOA mass-specific absorption cross sections (MAC) and refractive indices were calculated from real-time cavity ring-down photoacoustic spectrometry measurements at 405 and 532 nm and from UV-vis spectrometry measurements of methanol extracts of filter-collected particles (300 to 600 nm). At 405 nm, SOA MAC values and imaginary refractive indices increased with increasing oxidation level and decreased with increasing wavelength, leading to negligible absorption at 532 nm. Real refractive indices of SOA decreased with increasing oxidation level. Comparison with literature studies suggests that under typical polluted conditions the effect of NOx on SOA absorption is small. SOA may contribute significantly to atmospheric BrC, with the magnitude dependent on both precursor type and oxidation level. Mass-specific absorption cross sections (MAC) of SOA at λ = 405 nm as a function of the O/C ratio

  11. Remote Sensing of Spectral Aerosol Properties: A Classroom Experience

    NASA Technical Reports Server (NTRS)

    Levy, Robert C.; Pinker, Rachel T.

    2006-01-01

    Bridging the gap between current research and the classroom is a major challenge to today s instructor, especially in the sciences where progress happens quickly. NASA Goddard Space Flight Center and the University of Maryland teamed up in designing a graduate class project intended to provide a hands-on introduction to the physical basis for the retrieval of aerosol properties from state-of-the-art MODIS observations. Students learned to recognize spectral signatures of atmospheric aerosols and to perform spectral inversions. They became acquainted with the operational MODIS aerosol retrieval algorithm over oceans, and methods for its evaluation, including comparisons with groundbased AERONET sun-photometer data.

  12. Decadal changes in aerosol absorption across Brazil resulting from changes in biomass burning practices

    NASA Astrophysics Data System (ADS)

    Coe, H.; Morgan, W.; Darbyshire, E.; Allan, J. D.; Flynn, M.; Liu, D.; Langridge, J.; Johnson, B. T.; Haywood, J. M.; Longo, K.; Artaxo, P.; Highwood, E.; Mollard, J.

    2015-12-01

    Open biomass burning makes a substantial contribution to the global budget of black carbon, yet models significantly underestimate absorption aerosol optical depth compared to observations by approximately a factor of two over South America. These large differences need to be addressed. Recent work has shown that the number of deforestation fires has decreased across Amazonia over the last decade, giving rise to a decrease in the abundance of biomass burning aerosol across the region. At the same time there has been an increase in the frequency of agricultural burning across regions that have previously been deforested, as well as increased burning in the east of Brazil in the Cerrado regions. We sampled both of these types of open burning extensively during a recent aircraft experiment. Significant concentrations of organic carbon as well as black carbon were observed, with this ratio providing the main control on the single scattering albedo (SSA).Deforestation fires and wild forest fires are prevalent across the south west of the Amazon Basin, where smouldering burning dominates. In the east of Brazil, agricultural burning proceeds via a much more efficient form of combustion and as a result, black carbon is a much larger fraction of the aerosol mass and SSAs are much lower than in the west. We have analysed MISR data across the region to show that whilst aerosol optical depths have decreased during the dry season over the last decade, with greater rates of reduction occurring over the south western margins of Amazonia, absorption aerosol optical depths have significantly increased over the Cerrado and remained constant over south western Amazonia. This has led to a decline in SSA across the whole of the region with greater reductions occurring over the eastern states. This finding is consistent with our aircraft measurements. We will discuss the implications of these changes for air quality and climate across the region.

  13. Aerosol optical properties in pristine and biomass burning areas in the Amazon Basin

    NASA Astrophysics Data System (ADS)

    Artaxo, P.; Rizzo, L.; Lucca, S.; Paixao, M.; Sena, E. T.; Cirino, G.; Arana, A.

    2011-12-01

    Aerosol physical and chemical properties were measured in two sites in Amazonia. The clean site is at Central Amazonia, close to Manaus. A second sampling site is located in Porto Velho, Rondonia, an area strongly affected by biomass burning emissions. Long term measurements, from February 2008 are being carried out in these two sites. In the pristine central Amazonia, measurements were taken at the Cuieiras forest site, tower TT34, 55 Km North of Manaus under dry conditions (RH<40%). A MAAP 5012 absorption photometer in series with a nephelometer (TSI 3563) was used to measure aerosol absorption and scattering, respectively. Aerosol size distributions were measure using a TSI SMPS system. Aerosol composition, and several trace gases that helps to characterize aerosol sources were also measured. In Rondonia, a sampling station was installed close to the city of Porto Velho. Similar instrumentation as in Manaus was used in Rondonia. In the pristine Amazonian atmosphere, aerosol scattering coefficients ranged between 1 and 200 Mm-1 at 450 nm, while absorption ranged between 1 and 20 Mm-1 at 637 nm. A strong seasonal behavior was observed, with greater aerosol loadings during the dry season (Jul-Nov) as compared to the wet season (Dec-Jun). During the wet season in Manaus, aerosol scattering (450 nm) and absorption (637 nm) coefficients averaged, respectively, 14±22 and 0.9±0.8 Mm-1. Both optical coefficients were greatly increased during the dry season, averaging 58±35 Mm-1 and 4.1±3.8 Mm-1, correspondingly. Angstrom exponents for scattering were lower during the wet season (1.6±0.4) in comparison to the dry season (1.9±0.2), which is consistent with the shift from biomass burning aerosols. Single scattering albedo, calculated at 637 nm, did not show a significant seasonal variation, averaging 0.86 ± 0.06 and 0.86 ± 0.04, respectively for wet and dry season. In Rondonia, even in the wet season it was possible to observe a strong impact from anthropogenic

  14. Modelling the optical properties of aerosols in a chemical transport model

    NASA Astrophysics Data System (ADS)

    Andersson, E.; Kahnert, M.

    2015-12-01

    According to the IPCC fifth assessment report (2013), clouds and aerosols still contribute to the largest uncertainty when estimating and interpreting changes to the Earth's energy budget. Therefore, understanding the interaction between radiation and aerosols is both crucial for remote sensing observations and modelling the climate forcing arising from aerosols. Carbon particles are the largest contributor to the aerosol absorption of solar radiation, thereby enhancing the warming of the planet. Modelling the radiative properties of carbon particles is a hard task and involves many uncertainties arising from the difficulties of accounting for the morphologies and heterogeneous chemical composition of the particles. This study aims to compare two ways of modelling the optical properties of aerosols simulated by a chemical transport model. The first method models particle optical properties as homogeneous spheres and are externally mixed. This is a simple model that is particularly easy to use in data assimilation methods, since the optics model is linear. The second method involves a core-shell internal mixture of soot, where sulphate, nitrate, ammonia, organic carbon, sea salt, and water are contained in the shell. However, by contrast to previously used core-shell models, only part of the carbon is concentrated in the core, while the remaining part is homogeneously mixed with the shell. The chemical transport model (CTM) simulations are done regionally over Europe with the Multiple-scale Atmospheric Transport and CHemistry (MATCH) model, developed by the Swedish Meteorological and Hydrological Institute (SMHI). The MATCH model was run with both an aerosol dynamics module, called SALSA, and with a regular "bulk" approach, i.e., a mass transport model without aerosol dynamics. Two events from 2007 are used in the analysis, one with high (22/12-2007) and one with low (22/6-2007) levels of elemental carbon (EC) over Europe. The results of the study help to assess the

  15. Diurnal Cycles of Aerosol Optical Properties at Pico Tres Padres, Mexico City: Evidences for Changes in Particle Morphology and Secondary Aerosol Formation

    NASA Astrophysics Data System (ADS)

    Mazzoleni, C.; Dubey, M.; Chakrabarty, R.; Moosmuller, H.; Onasch, T.; Zavala, M.; Herndon, S.; Kolb, C.

    2007-12-01

    Aerosol optical properties affect planetary radiative balance and depend on chemical composition, size distribution, and morphology. During the MILAGRO field campaign, we measured aerosol absorption and scattering in Mexico City using the Los Alamos aerosol photoacoustic (LAPA) instrument operating at 781 nm. The LAPA was mounted on-board the Aerodyne Research Inc. mobile laboratory, which hosted a variety of gaseous and aerosol instruments. During the campaign, the laboratory was moved to different sites, capturing spatial and temporal variability. Additionally, we collected ambient aerosols on Nuclepore filters for scanning electron microscopy (SEM) analysis. SEM images of selected filters were taken to study particle morphology. Between March 7th and 19th air was sampled at the top of Pico Tres Padres, a mountain on the north side of Mexico City. Aerosol absorption and scattering followed diurnal patterns related to boundary layer height and solar insulation. We report an analysis of aerosol absorption, scattering, and morphology for three days (9th, 11th and 12th of March 2006). The single scattering albedo (SSA, ratio of scattering to total extinction) showed a drop in the tens-of-minutes-to-hour time frame after the boundary layer grew above the sampling site. Later in the day the SSA rose steadily reaching a maximum in the afternoon. The SEM images showed a variety of aerosol shapes including fractal-like aggregates, spherical particles, and other shapes. The absorption correlated with the CO2 signal and qualitatively with the fraction of fractal-like particles to the total particle count. In the afternoon the SSA qualitatively correlated with a relative increase in spherical particles and total particle count. These observed changes in optical properties and morphology can be explained by the dominant contribution of freshly emitted particles in the morning and by secondary particle formation in the afternoon. SSA hourly averaged values ranged from ~0.63 in

  16. Absorption, scattering and single scattering albedo of aerosols obtained from in situ measurements in the subarctic coastal region of Norway

    NASA Astrophysics Data System (ADS)

    Montilla, E.; Mogo, S.; Cachorro, V.; Lopez, J.; de Frutos, A.

    2011-01-01

    In situ measurements of aerosol optical properties were made in summer 2008 at the ALOMAR station facility (69°16 N, 16°00 E), located at a rural site in the North of the island of Andøya (Vesterålen archipelago), about 300 km north of the Arctic Circle. The extended three months campaign was part of the POLAR-CAT Project of the International Polar Year (IPY-2007-2008), and its goal was to characterize the aerosols of this sub-Arctic area which frequently transporte to the Arctic region. The ambient light-scattering coefficient, σs(550 nm), at ALOMAR had a hourly mean value of 5.412 Mm-1 (StD = 3.545 Mm-1) and the light-absorption coefficient, σa(550 nm), had an hourly mean value of 0.400 Mm-1 (StD = 0.273 Mm-1). The scattering/absorption Ångström exponents, αs,a, are used for detailed analysis of the variations of the spectral shape of σs,a. The single scattering albedo, &omega0, ranges from 0.622 to 0.985 (mean = 0.913, StD = 0.052) and the relation of this property to the absorption/scattering coefficients and the Ångström exponents is presented. The relationships between all the parameters analyzed, mainly those related to the single scattering albedo, allow us to describe the local atmosphere as extremely clean.

  17. Interpreting the Ultraviolet Aerosol Index Observed with the OMI Satellite Instrument to Understand Absorption by Organic Aerosols: Implications for Atmospheric Oxidation and Direct Radiative Effects

    NASA Technical Reports Server (NTRS)

    Hammer, Melanie S.; Martin, Randall V.; Donkelaar, Aaron van; Buchard, Virginie; Torres, Omar; Ridley, David A.; Spurr, Robert J. D.

    2016-01-01

    Satellite observations of the ultraviolet aerosol index (UVAI) are sensitive to absorption of solar radiation by aerosols; this absorption affects photolysis frequencies and radiative forcing. We develop a global simulation of the UVAI using the 3-D chemical transport model GEOSChem coupled with the Vector Linearized Discrete Ordinate Radiative Transfer model (VLIDORT). The simulation is applied to interpret UVAI observations from the Ozone Monitoring Instrument (OMI) for the year 2007. Simulated and observed values are highly consistent in regions where mineral dust dominates the UVAI, but a large negative bias (-0.32 to -0.97) exists between simulated and observed values in biomass burning regions. We determine effective optical properties for absorbing organic aerosol, known as brown carbon (BrC), and implement them into GEOS-Chem to better represent observed UVAI values over biomass burning regions. The inclusion of absorbing BrC decreases the mean bias between simulated and OMI UVAI values from -0.57 to -0.09 over West Africa in January, from -0.32 to +0.0002 over South Asia in April, from -0.97 to -0.22 over southern Africa in July, and from -0.50 to +0.33 over South America in September. The spectral dependence of absorption after including BrC in the model is broadly consistent with reported observations for biomass burning aerosol, with absorbing Angstrom exponent (AAE) values ranging from 2.9 in the ultraviolet (UV) to 1.3 across the UV-Near IR spectrum. We assess the effect of the additional UV absorption by BrC on atmospheric photochemistry by examining tropospheric hydroxyl radical (OH) concentrations in GEOS-Chem. The inclusion of BrC decreases OH by up to 30% over South America in September, up to 20% over southern Africa in July, and up to 15% over other biomass burning regions. Global annual mean OH concentrations in GEOS-Chem decrease due to the presence of absorbing BrC, increasing the methyl chloroform lifetime from 5.62 to 5.68 years, thus

  18. Aerosol particle properties in a South American megacity

    NASA Astrophysics Data System (ADS)

    Ulke, Ana; Torres-Brizuela, Marcela; Raga, Graciela; Baumgardner, Darrel; Cancelada, Marcela

    2015-04-01

    The subtropical city of Buenos Aires is located on the western shore of Río de la Plata, on the southeastern coast of Argentina. It is the second largest metropolitan area in South America, with a population density of around 14 thousand people per km2. When all 24 counties of the Great Buenos Aires Metropolitan Area are included it is the third-largest conurbation in Latin America, with a population of around fifteen million inhabitants. The generalized worldwide trend to concentrate human activities in urban regions that continue to expand in area, threatens the local and regional environment. Air pollution in the Buenos Aires airshed is due to local sources (mainly the mobile sources, followed by the electric power plants and some industries) and to distant sources (like biomass burning, dust, marine aerosols and occasionally volcanic ash) whose products arrive in the city area due to the regional transport patterns. Previous research suggests that ambient aerosol particle concentrations should be considered an air quality problem. A field campaign was conducted in Buenos Aires in 2011 in order to characterize some aerosol particles properties measured for the first time in the city. Measurements began in mid- April and continued until December. The field observations were done in a collaborative effort between the Universities of Mexico (UNAM) and Buenos Aires (UBA). A suite of instruments was installed on the roof of an UBA laboratory and classroom buildings (34.54° S, 58.44° W) at an altitude of approximately 30 m above sea level. The measurements included the number concentration of condensation nuclei (CN) larger than approximately 50 nm, the mass concentration of particle-bound polycyclic aromatic hydrocarbons (PPAH), the scattering (Bscat) and absorption (Babs) coefficients at 550 nm and the vertical profiles of backscattered light from aerosols at a wavelength of 910 nm using a ceilometer. In addition, a weather station recorded the meteorological

  19. Long-term Observation of Aerosol Optical Properties at the SORPES station in Nanjing, China

    NASA Astrophysics Data System (ADS)

    Shen, Yicheng; Ding, Aijun; Virkkula, Aki; Wang, Jiaping; Chi, Xuguang; Qi, Ximeng; Liu, Qiang; Zheng, Longfei; Xie, Yuning

    2016-04-01

    Atmospheric aerosols influence the earth's radiation budget by scattering and absorbing solar radiation and contribute substantial uncertainty in the estimation of climate forcing. Thorough and comprehensive measurements on different parameters including absorption and scattering coefficient, wavelength dependence and angular dependence along with their daily and seasonal variation help to understand the influence of aerosol on radiation. 2-years continuous measurement of aerosol optical properties has been conducted from June 2013 to May 2015 at the Station for Observing Regional Process of Earth System (SORPES) station, which is a regional background station located in downwind direction of Yangtze River Delta (YRD) urban agglomeration in China. A 7-wavelenths aethalometer and a 3-wavelenths nephelometer were used to measure absorption and scattering coefficient, and also other parameters like single scattering albedo (SSA), absorption angstrom Exponent (AAE), scattering angstrom exponent (SAE) and back-scattering refraction. In addtion, simultaneous measurements on chemical composition and particle size distribution were performed so as to investigate the dependencies of aerosol optical properties on chemical composition and size distribution. To get further insight on the influencing factors, Lagrangian particle dispersion modeling (LPDM) was employed for source identification in this study. The averages of absorption coefficient, scattering coefficient and SSA are 26.0±18.7 Mm-1, 426±327 Mm-1 , 0.936±0.3 at 520nm respectively for whole period. SAE between 450 and 635nm is 1.299±0.34 and have strong negative correlation with particle Surface Mean Diameter (SMD). AAE between 370 and 950nm is 1.043±0.15 for whole period but growth to more than 1.6 in all identified Biomass Burning (BB) events.

  20. Compositional and Optical Properties of Titan Haze Analogs Using Aerosol Mass Spectrometry, Photoacoustic Spectroscopy and Cavity Ring-Down Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ugelow, M.; Zarzana, K. J.; Tolbert, M. A.

    2015-12-01

    The organic haze that surrounds Saturn's moon Titan is formed through the photolysis and electron initiated dissociation of methane and nitrogen. The chemical pathways leading to haze formation and the resulting haze optical properties are still highly uncertain. Here we examine the compositional and optical properties of Titan haze aerosol analogs. By studying these properties together, the impact of haze on Titan's radiative balance can be better understood. The aerosol analogs studied are produced from different initial methane concentrations (0.1, 2 and 10% CH4) using spark discharge excitation. To determine the complex refractive index of the aerosol, we combine two spectroscopic techniques, one that measures absorption and one that measures extinction: photoacoustic spectroscopy coupled with cavity ring-down spectroscopy (PASCaRD). This technique provides the benefit of a high precision determination of the imaginary component of the refractive index (k), along with the highly sensitive determination of the real component of the refractive index (n). The refractive indices are retrieved at two wavelengths, 405 and 532 nm, using the PASCaRD system. To yield aerosol composition, quadrupole aerosol mass spectrometry is used. Compositional information is obtained from a technique that uses isotopically labeled and unlabeled methane gas. I will present preliminary data on the complex refractive indices of Titan aerosol analogs at both wavelengths, in conjunction with the aerosol composition as a percent by weight of carbon, nitrogen and hydrogen. The correlation of optical and chemical properties should be useful for remote sensing instruments probing Titan haze.

  1. The Measurement of Aerosol Optical Properties using Continuous Wave Cavity Ring-Down Techniques

    NASA Technical Reports Server (NTRS)

    Strawa, Anthony W.; Castaneda, Rene; Owano, Thomas; Baer, Douglas S.; Paldus, Barbara A.; Gore, Warren J. (Technical Monitor)

    2002-01-01

    Large uncertainties in the effects that aerosols have on climate require improved in situ measurements of extinction coefficient and single-scattering albedo. This paper describes the use of continuous wave cavity ring-down (CW-CRD) technology to address this problem. The innovations in this instrument are the use of CW-CRD to measure aerosol extinction coefficient, the simultaneous measurement of scattering coefficient, and small size suitable for a wide range of aircraft applications. Our prototype instrument measures extinction and scattering coefficient at 690 nm and extinction coefficient at 1550 nm. The instrument itself is small (60 x 48 x 15 cm) and relatively insensitive to vibrations. The prototype instrument has been tested in our lab and used in the field. While improvements in performance are needed, the prototype has been shown to make accurate and sensitive measurements of extinction and scattering coefficients. Combining these two parameters, one can obtain the single-scattering albedo and absorption coefficient, both important aerosol properties. The use of two wavelengths also allows us to obtain a quantitative idea of the size of the aerosol through the Angstrom exponent. Minimum sensitivity of the prototype instrument is 1.5 x 10(exp -6)/m (1.5 M/m). Validation of the measurement of extinction coefficient has been accomplished by comparing the measurement of calibration spheres with Mie calculations. This instrument and its successors have potential to help reduce uncertainty currently associated with aerosol optical properties and their spatial and temporal variation. Possible applications include studies of visibility, climate forcing by aerosol, and the validation of aerosol retrieval schemes from satellite data.

  2. The Measurement of Aerosol Optical Properties Using Continuous Wave Cavity Ring-Down Techniques

    NASA Technical Reports Server (NTRS)

    Strawa, A. W.; Owano, T.; Castaneda, R.; Baer, D. S.; Paldus, B. A.; Gore, Warren J. (Technical Monitor)

    2002-01-01

    Large uncertainties in the effects that aerosols have on climate require improved in-situ measurements of extinction coefficient and single-scattering albedo. This abstract describes the use of continuous wave cavity ring-down (CW-CRD) technology to address this problem. The innovations in this instrument are the use of CW-CRD to measure aerosol extinction coefficient, the simultaneous measurement of scattering coefficient, and small size suitable for a wide range of aircraft applications. Our prototype instrument measures extinction and scattering coefficient at 690 nm and extinction coefficient at 1550 nm. The instrument itself is small (60 x 48 x 15 cm) and relatively insensitive to vibrations. The prototype instrument has been tested in our lab and used in the field. While improvements in performance are needed, the prototype has been shown to make accurate and sensitive measurements of extinction and scattering coefficients. Combining these two parameters, one can obtain the single-scattering albedo and absorption coefficient, both important aerosol properties. The use of two wavelengths also allows us to obtain a quantitative idea of the size of the aerosol through the Angstrom exponent. Minimum sensitivity of the prototype instrument is 1.5 x 10(exp -6)/m (1.5/Mm). Validation of the measurement of extinction coefficient has been accomplished by comparing the measurement of calibration spheres with Mie calculations. This instrument and its successors have potential to help reduce uncertainty currently associated with aerosol optical properties and their spatial and temporal variation. Possible applications include studies of visibility, climate forcing by aerosol, and the validation of aerosol retrieval schemes from satellite data.

  3. Improving satellite retrieved aerosol microphysical properties using GOCART data

    NASA Astrophysics Data System (ADS)

    Li, S.; Kahn, R.; Chin, M.; Garay, M. J.; Chen, L.; Liu, Y.

    2014-09-01

    The Multi-Angle Imaging Spectro-Radiometer (MISR) instrument on NASA's Terra satellite can provide more reliable Aerosol Optical Depth (AOD, τ) and more particle information, such as constraints on particle size (Angström exponent or ANG, α), particle shape, and single-scattering albedo (SSA, ω), than many other satellite instruments. However, MISR's ability to retrieve aerosol properties is weakened at low AOD levels. When aerosol-type information content is low, many candidate aerosol mixtures can match the observed radiances. We propose an algorithm to improve MISR aerosol retrievals by constraining MISR mixtures' ANG and absorbing AOD (AAOD) with Goddard Chemistry Aerosol Radiation and Transport (GOCART) model-simulated aerosol properties. To demonstrate this approach, we calculated MISR aerosol optical properties over the contiguous US from 2006 to 2009. Sensitivities associated with the thresholds of MISR-GOCART differences were analyzed according to the agreement between our results (AOD, ANG, and AAOD) and AErosol RObotic NETwork (AERONET) observations. Overall, our AOD has a good agreement with AERONET because the MISR AOD retrieval is not sensitive to different mixtures under many retrieval conditions. The correlation coefficient (r) between our ANG and AERONET improves to 0.45 from 0.29 for the MISR Version 22 standard product and 0.43 for GOCART when all data points are included. However, when only cases having AOD > 0.2, the MISR product itself has r ~ 0.40, and when only AOD > 0.2 and the best-fitting mixture are considered, r ~ 0.49. So as expected, the ANG improvement occurs primarily when the model constraint is applied in cases where the particle type information content of the MISR radiances is low. Regression analysis for AAOD shows that MISR Version 22 and GOCART misestimate AERONET by a ratio (mean retrieved AAOD to mean AERONET AAOD) of 0.5; our method improves this ratio to 0.74. Large discrepancies are found through an inter

  4. Wavelength dependence of aerosol light absorption in urban and biomass burning impacted conditions: An integrative perspective

    NASA Astrophysics Data System (ADS)

    Arnott, W. P.; Gyawali, M.; Lewis, K.; Moosmuller, H.

    2009-12-01

    Aerosol light absorption depends on aerosol size, morphology, mixing state, and composition. The wavelength dependence is often characterized with use of the Angstrom coefficient for absorption (AAE) determined from measurements at two or more wavelengths. Low fractal dimension black carbon (BC) particles are often expected to have an AAE near unity. Values of AAE significantly larger than unity are often attributed to the presence of an organic coating that absorbs strongly at lower wavelengths, though we have found that even non absorbing coatings on small, biomass burning related BC cores can have large AAE. Values of AAE significantly less than unity are often ascribed to experimental errors or large particle sizes, however, we find that they are most commonly associated with modest absorbing or non absorbing organic coatings that collapse the fractal soot BC core in urban aerosol to a dimension near that of a sphere. Photoacoustic measurements at 405 nm, 532 nm, 870 nm, and 1047 nm in urban Reno and Las Vegas NV, and for biomass burning experiments are used presented to illustrate the range of AAE possible, and coated sphere modeling results are presented to interpret the measurements.

  5. Determination of the broadband optical properties of biomass burning aerosol

    NASA Astrophysics Data System (ADS)

    Bluvshtein, Nir; Flores, J. Michel; Segev, Lior; Lin, Peng; Laskin, Alexander; Rudich, Yinon

    2016-04-01

    The direct and semi-direct effects of atmospheric aerosol on the Earth's energy balance are still the two of the largest uncertainties in our understanding of anthropogenic radiative forcing. In this study we developed a new approach for determining high sensitivity broadband UV-Vis spectrum (300-650 nm) of extinction, scattering and absorption coefficients, single scattering albedo and the complex refractive index for continuous, spectral and time dependent, monitoring of polydisperse aerosols population. This new approach was applied in a study of biomass burning aerosol. Extinction, scattering and absorption coefficients (αext, αsca, αabs, respectively) were continually monitored using photoacoustic spectrometer coupled to a cavity ring down spectrometer (PA-CRD-AS) at 404 nm, a dual-channel Broadband cavity-enhanced spectrometer (BBCES) at 315-345 nm and 390-420 nm and a three channel integrating nephelometer (IN) centered at 457, 525 and 637 nm. During the biomass burning event, the measured aerosol number concentration increased by more than an order of magnitude relative to other week nights and the mode of the aerosols size distribution increased from 40-50 nm to 110nm diameter. αext and αsca increased by a factor of about 5.5 and 4.5, respectively. The αabs increased by a factor over 20, indicating a significant change in the aerosol overall chemical composition. The imaginary part of the complex RI at 404nm increased from its background level at about 0.02 to a peak of about 0.08 and the SSA decreased from 0.9 to about 0.6. Significant change of the absorption spectral dependence indicates formation of visible-light absorbing compounds. The mass absorption cross section of the water soluble organic aerosol (MACWSOA) reached up to about 12% of the corresponding value for black carbon (BC) at 450 nm and up to 30% at 300 nm. These results demonstrate the importance of biomass burning in understanding global and regional radiative forcing.

  6. The thermal infrared radiance properties of dust aerosol over ocean

    NASA Astrophysics Data System (ADS)

    Hao, Zengzhou; Pan, Delu; Tu, Qianguang; Gong, Fang; Chen, Jianyu

    2015-10-01

    Asian dust storms, which can long-range transport to ocean, often occur on spring. The present of Asian dust aerosols over ocean makes some difficult for other studies, such as cloud detection, and also take some advantage for ocean, such as take nutrition into the ocean by dry or wet deposition. Therefore, it is important to study the dust aerosol and retrieve the properties of dust from satellite observations that is mainly from the thermal infrared radiance. In this paper, the thermal infrared radiance properties of dust aerosol over ocean are analyzed from MODIS and MTSAT2 observations and Streamer model simulations. By analyzing some line samples and a series of dust aerosol region, it shows that the dust aerosol brightness temperature at 12μm (BT12) is always greater than BT11 and BT8.5, and BT8.5 is general greater than BT11. The brightness temperature different between 11μm and 12μm (BTD11-12) increases with the dust intensity. And the BTD11-12 will become positive when the atmospheric relative humidity is greater than 70%. The BTD11-12 increases gradually with the surface temperature while the effect on BTD11-12 of dust layer temperature is not evident. Those are caused by the transmission of the dust aerosol is different at the two thermal infrared channels. During daytime, dust infrared brightness temperature at mid-infrared bands should reduce the visual radiance, which takes about 25K or less. In general, BT3.7 is greater than BT11 for dust aerosol. Those results are helpful to monitor or retrieve dust aerosol physical properties over ocean from satellite.

  7. THERMAL PROPERTIES OF SECONDARY ORGANIC AEROSOLS

    EPA Science Inventory

    Volume concentrations of steady-state secondary organic aerosol (SOA) were measured in several hydrocarbon/NOx irradiation experiments. These measurements were used to estimate the thermal behavior of the particles that may be formed in the atmosphere. These laborator...

  8. In situ observations of aerosol physical and optical properties in northern India

    NASA Astrophysics Data System (ADS)

    Lihavainen, H.; Hyvarinen, A.; Hooda, R. K.; Raatikainen, T. E.; Sharma, V.; Komppula, M.

    2012-12-01

    The southern Asia, including India, is exposed to substantial quantities of particulate air pollution originating mainly from fossil fuel combustion and biomass burning. Besides serious adverse health effects, these aerosols cause a large reduction of solar radiation at the surface accompanied by a substantial atmospheric heating, which is expected to have significant influences on the air temperature, crop yields, livestock and water resources over the southern Asia. The various influences by aerosols in this region depend crucially on the development of aerosol emissions from household, industrial, transportation and biomass burning sectors. The main purpose of this study is to investigate several measured aerosol optical and physical properties. We take advantage of observations from two measurement stations which have been established by the Finnish Meteorological Institute and The Energy and Resources Institute. Another station is on the foothills of Himalayas, in Mukteshwar, about 350 km east of New Delhi at elevation about 2 km ASL. This site is considered as a rural background site. Measurements of aerosol size distribution (7-500 nm), PM10, PM2.5, aerosol scattering and absorption coefficients and weather parameters have been conducted since 2006. Another station is located at the outskirts of New Delhi, in Gual Pahari, about 35 km south of city centre. It is considered as an urban background site. Measurements of aerosol size distribution (7 nm- 10 μm), PM10, PM2.5, aerosol scattering and absorption coefficients, aerosol optical depth, aerosol vertical distribution (LIDAR), aerosol filter sampling for chemical characterization and weather parameters were conducted between 2008 and 2010. On the overall average PM10 and PM2.5 values were about 3-4 times higher in Gual Pahari than in Mukteshwar as expected, 216 and 126 μg m^-3, respectively. However, difference depended much on the season, so that during winter time PM10 and PM2.5 concentrations were about

  9. Measuring Aerosol Optical Properties with the Ozone Monitoring Instrument (OMI)

    NASA Technical Reports Server (NTRS)

    Veefkind, J. P.; Torres, O.; Syniuk, A.; Decae, R.; deLeeuw, G.

    2003-01-01

    The Ozone Monitoring Instrument (OMI) is the Dutch-Finnish contribution to the NASA EOS-Aura mission scheduled for launch in January 2004. OM1 is an imaging spectrometer that will measure the back-scattered Solar radiance between 270 an 500 nm. With its relatively high spatial resolution (13x24 sq km at nadir) and daily global coverage. OM1 will make a major contribution to our understanding of atmospheric chemistry and to climate research. OM1 will provide data continuity with the TOMS instruments. One of the pleasant surprises of the TOMS data record was its information on aerosol properties. First, only the absorbing aerosol index, which is sensitive to elevated lay- ers of aerosols such as desert dust and smoke aerosols, was derived. Recently these methods were further improved to yield aerosol optical thickness and single scattering albedo over land and ocean for 19 years of TOMS data (1979-1992,1997-2002), making it one of the longest and most valuable time series for aerosols presently available. Such long time series are essential to quantify the effect of aerosols on the Earth& climate. The OM1 instrument is better suited to measure aerosols than the TOMS instruments because of the smaller footprint, and better spectral coverage. The better capabilities of OMI will enable us to provide an improved aerosol product, but the knowledge will also be used for further analysis of the aerosol record from TOMS. The OM1 aerosol product that is currently being developed for OM1 combines the TOMS experience and the multi-spectral techniques that are used in the visible and near infrared. The challenge for this new product is to provide aerosol optical thickness and single scattering albedo from the near ultraviolet to the visible (330-500 nm) over land and ocean. In this presentation the methods for deriving the OM1 aerosol product will be presented. Part of these methods developed for OM1 can already be applied to TOMS data and results of such analysis will be shown.

  10. Light-absorbing Aerosol Properties in the Kathmandu Valley during SusKat-ABC Field Campaign

    NASA Astrophysics Data System (ADS)

    Kim, S.; Yoon, S.; Kim, J.; Cho, C.; Jung, J.

    2013-12-01

    Light-absorbing aerosols, such as black carbon (BC), are major contributors to the atmospheric heating and the reduction of solar radiation reaching at the earth's surface. In this study, we investigate light-absorption and scattering properties of aerosols (i.e., BC mass concentration, aerosol solar-absorption/scattering efficiency) in the Kathmandu valley during Sustainable atmosphere for the Kathmandu valley (SusKat)-ABC campaign, from December 2012 to February 2013. Kathmandu City is among the most polluted cities in the world. However, there are only few past studies that provide basic understanding of air pollution in the Kathmandu Valley, which is not sufficient for designing effective mitigation measures (e.g., technological, financial, regulatory, legal and political measures, planning strategies). A distinct diurnal variation of BC mass concentration with two high peaks observed during wintertime dry monsoon period. BC mass concentration was found to be maximum around 09:00 and 20:00 local standard time (LST). Increased cars and cooking activities including substantial burning of wood and other biomass in the morning and in the evening contributed to high BC concentration. Low BC concentrations during the daytime can be explain by reduced vehicular movement and cooking activities. Also, the developmements of the boundary layer height and mountain-valley winds in the Kathmandu Valley paly a crucial role in the temproal variation of BC mass concentrations. Detailed radiative effects of light-absorbing aerosols will be presented.

  11. Measurement of Gas and Aerosol Phase Absorption Spectra across the Visible and Near-IR Using Supercontinuum Photoacoustic Spectroscopy.

    PubMed

    Radney, James G; Zangmeister, Christopher D

    2015-07-21

    We demonstrate a method to measure the absorption spectra of gas and aerosol species across the visible and near-IR (500 to 840 nm) using a photoacoustic (PA) spectrometer and a pulsed supercontinuum laser source. Measurements of gas phase absorption spectra were demonstrated using H2O(g) as a function of relative humidity (RH). The measured absorption intensities and peak shapes were able to be quantified and compared to spectra calculated using the 2012 High Resolution Transmission (HITRAN2012) database. Size and mass selected nigrosin aerosol was used to measure absorption spectra across the visible and near-IR. Spectra were measured as a function of aerosol size/mass and show good agreement to Mie theory calculations. Lastly, we measured the broadband absorption spectrum of flame generated soot aerosol at 5% and 70% RH. For the high RH case, we are able to quantifiably separate the soot and water absorption contributions. For soot, we observe an enhancement in the mass specific absorption cross section ranging from 1.5 at 500 nm (p < 0.01) to 1.2 at 840 nm (p < 0.2) and a concomitant increase in the absorption Ångström exponent from 1.2 ± 0.4 (5% RH) to 1.6 ± 0.3 (70% RH). PMID:26098142

  12. AN INTERCOMPARISON CF THE INTEGRATING PLATE AND THE LASER TRANSMISSION METHODS FOR DETERMINATION OF AEROSOL ABSORPTION COEFFICIENTS

    SciTech Connect

    Sadler, M.; Charlson, R.J.; Rosen, H.; Novakov, T.

    1980-07-01

    The absorption coefficients determined by the integrating plate method and the laser transmission method are found to be comparable and highly correlated. Furthermore, a high correlation is found between these absorption coefficients and the carbon content of the aerosol in urbanized regions.

  13. Linking aerosol size and optical properties to trace gases emitted from biomass burning in real-time

    NASA Astrophysics Data System (ADS)

    McMeeking, G. R.; Carrico, C. M.; Stockwell, C.; Yokelson, R. J.; Veres, P. R.; DeMott, P. J.; Kreidenweis, S. M.

    2014-12-01

    Biomass burning aerosols have large impacts on regional and global climate that are partly determined by their optical properties. The optical properties of aerosol depend on their size and composition, which in turn are related to fire combustion processes. Here we investigate relationships between a large suite of trace gases and aerosol size and optical properties to better understand processes governing the optical properties of fresh biomass burning aerosol emissions. We examined over 100 individual burns of biomass fuels during the Fire Laboratory at Missoula Experiment 4 (FLAME 4). Emissions were measured directly from an exhaust stack designed to capture all emissions from relatively small-scale fires burned at the base of a large burn chamber. Trace gas species were measured using a combination of an open-path Fourier transform infrared spectrometer (OP-FTIR) and proton-transfer mass spectrometer (PTR-MS). Aerosol optical properties at 870 nm were measured using a photoacoustic extinctiometer (PAX) and particle size distributions were measured using a Fast Mobility Particle Sizer (FMPS) and Aerodynamic Particle Sizer. The rapid response of the instruments allowed for comparisons of the emissions and particle properties over the duration of the fire. For example, we observed correlations between aerosol absorption, particle size, and gas-phase species associated with different types of combustion such as flaming and smoldering. We also report fire-integrated emissions for aerosol absorption and scattering coefficients and compare these to other fire-integrated properties. Many of our burn experiments examined a number of fuels that had not before been characterized in laboratory conditions, including a number of peat fuels, African savanna grasses and crop residuals.

  14. International Workshop on Stratospheric Aerosols: Measurements, Properties, and Effects

    NASA Technical Reports Server (NTRS)

    Pueschel, Rudolf F. (Editor)

    1991-01-01

    Following a mandate by the International Aerosol Climatology Program under the auspices of International Association of Meteorology and Atmospheric Physics International Radiation Commission, 45 scientists from five nations convened to discuss relevant issues associated with the measurement, properties, and effects of stratospheric aerosols. A summary is presented of the discussions on formation and evolution, transport and fate, effects on climate, role in heterogeneous chemistry, and validation of lidar and satellite remote sensing of stratospheric aerosols. Measurements are recommended of the natural (background) and the volcanically enhanced aerosol (sulfuric acid and silica particles), the exhaust of shuttle, civil aviation and supersonic aircraft operations (alumina, soot, and ice particles), and polar stratospheric clouds (ice, condensed nitric and hydrochloric acids).

  15. Aerosol Radiative Forcing Derived From SeaWIFS - Retrieved Aerosol Optical Properties

    NASA Technical Reports Server (NTRS)

    Chou, Mong-Dah; Chan, Pui-King; Wang, Menghua; Einaudi, Franco (Technical Monitor)

    2000-01-01

    To understand climatic implications of aerosols over global oceans, the aerosol optical properties retrieved from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) are analyzed, and the effects of the aerosols on the Earth's radiation budgets (aerosol radiative forcing, ARF) are computed using a radiative transfer model. It is found that the distribution of the SeaWiFS-retrieved aerosol optical thickness is distinctively zonal. The maximum in the equatorial region coincides with the Intertropical Convergence Zone, and the maximum in the Southern Hemispheric high latitudes coincides with the region of prevailing westerlies. The minimum aerosol optical thickness is found in the subtropical high pressure regions, especially in the Southern Hemisphere. These zonal patterns clearly demonstrate the influence of atmospheric circulation on the oceanic aerosol distribution. Over global oceans, aerosols reduce the annual mean net downward solar flux by 5.4 W m-2 at the top of the atmosphere and by 6.1 W m-2 at the surface. The largest ARF is found in the tropical Atlantic, Arabian Sea, Bay of Bengal, the coastal regions of Southeast and East Asia, and the Southern Hemispheric high latitudes. During the period of the Indonesian big fires (September-December 1997), the cooling due to aerosols is greater than 15 W m-2 at the top of the atmosphere and greater than 30 W m(exp -1) at the surface in the vicinity of the maritime continents. The atmosphere receives extra solar radiation by greater than 15 W m(exp -1) over a large area. These large changes in radiative fluxes are expected to have enhanced the atmospheric stability, weakened the atmospheric circulation, and augmented the drought condition during that period. It would be very instructive to simulate the regional climatic. The model-calculated clear sky solar flux at the top of the atmosphere is compared with that derived from the Clouds and the Earth's Radiant Energy System (CERES). The net downward solar flux of

  16. Aerosol Properties and Radiative Forcing over Kanpur during Severe Aerosol Loading Conditions

    SciTech Connect

    Kaskaoutis, D. G.; Sinha, P. R.; Vinoj, V.; Kosmopoulos, P. G.; Tripathi, S. N.; Misra, Amit; Sharma, M.; Singh, R. P.

    2013-11-01

    Atmospheric aerosols over India exhibit large spatio-temporal fluctuation driven by the local monsoon system, emission rates and seasonally-changed air masses. The northern part of India is well-known for its high aerosol loading throughout the year due to anthropogenic emissions, dust influence and biomass burning. On certain circumstances and, under favorable weather conditions, the aerosol load can be severe, causing significant health concerns and climate implications. The present work analyzes the aerosol episode (AE) days and examines the modification in aerosol properties and radiative forcing during the period 2001-2010 based on Kanpur-AERONET sun photometer data. As AEs are considered the days having daily-mean aerosol optical depth (AOD) above the decadal mean + 1 STD (standard deviation); the threshold value is defined at 0.928. The results identify 277 out of 2095 days (13.2%) of AEs over Kanpur, which are most frequently observed during post-monsoon (78 cases, 18.6%) and monsoon (76, 14.7%) seasons due to biomass-burning episodes and dust influence, respectively. On the other hand, the AEs in winter and pre-monsoon are lower in both absolute and percentage values (65, 12.5% and 58, 9.1%, respectively). The modification in aerosol properties on the AE days is strongly related to season. Thus, in post-monsoon and winter the AEs are associated with enhanced presence of fine-mode aerosols and Black Carbon from anthropogenic pollution and any kind of burning, while in pre-monsoon and monsoon seasons they are mostly associated with transported dust. Aerosol radiative forcing (ARF) calculated using SBDART shows much more surface (~-69 to -97 Wm-2) and Top of Atmosphere cooling (-20 to -30 Wm-2) as well as atmospheric heating (~43 to 71 Wm-2) during the AE days compared to seasonal means. These forcing values are mainly controlled by the higher AODs and the modified aerosol characteristics (Angstrom α, SSA) during the AE days in each season and may cause

  17. Global dust infrared aerosol properties retrieved using hyperspectral sounders

    NASA Astrophysics Data System (ADS)

    Capelle, Virginie; Chédin, alain; Pondrom, Marc; Pierangelo, Clémence; Armante, Raymond; Crevoisier, Cyril; Crépeau, Laurent; Scott, Noëlle

    2015-04-01

    Observations from infrared hyperspectral sounders, here IASI and AIRS, are interpreted in terms of dust aerosol properties (AOD and mean altitude). The method is based on a "Look-Up-Table" (LUT) approach, where all radiative transfer computation is performed once for all and "off-line", for a large selection of atmospheric situations, of observing conditions, of surface characteristics (in particular the surface emissivity and temperature), and different aerosol refractive index models. The inversion scheme follows two main steps: first, determination of the observed atmospheric thermodynamic situation, second, simultaneous retrieval of the 10µm coarse-mode AOD and of the mean altitude. The method is here applied over sea and over land, at daily scale daytime and nighttime, and at the satellite pixel resolution (12 km at nadir). The geographical study area studied includes the northern tropics from west Atlantic to the Arabian peninsula and Indian ocean, and the Mediterranean basin, all of them characterized by strong, regular dust events. A special focus is given to the hourly variation of aerosol properties within a day. In this context, both IASI overpasses are processed, providing two measurements at 9:30AM and 9:30PM (equator local time) each day. First results obtained from AIRS observations, made at 1:30 AM and PM, open the way to the analysis of the aerosol diurnal cycle. For the AOD, comparisons are made with AERONET ground-based data , when available, in order to 1) evaluate our results, and 2) show the importance of a better knowledge of the aerosol diurnal cycle, especially close to the sources. Mean aerosol layer altitude obtained from IASI is compared at local scale with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP/CALIPSO) aerosol altitude.

  18. Optical Properties of Polymers Relevant to Secondary Organic Aerosols

    NASA Astrophysics Data System (ADS)

    Marrero-Ortiz, W.; Gomez-Hernandez, M. E.; Xu, W.; Guo, S.; Zhang, R.

    2014-12-01

    Atmospheric aerosols play a critical role in climate directly by scattering and absorbing solar radiation and indirectly by modifying the cloud formation. Currently, the direct and indirect effects of aerosols represent the largest uncertainty in climate predictions models. Some aerosols are directly emitted, but the majority are formed in the atmosphere by the oxidation of gaseous precursors. However, the formation of aerosols at the molecular level is not fully characterized. Certain category of secondary organic aerosols (SOA), which represent a significant fraction of the total aerosol burden, can be light-absorbing, also known as brown carbon. However, the overall contribution of SOA to the brown carbon and the related climate forcing is poorly understood. Such incomplete understanding is due in part to the chemical complexity of SOA and the lack of knowledge regarding SOA formation, transformation, and optical properties. Based on previous laboratory experiments, field measurements, and modeling studies, it has been suggested that the polymers and oligomers play an important role in the SOA formation. Atmospheric polymers could be produced by the hydration or heterogeneous reactions of epoxides and small α-dicarbonyls. Their aqueous chemistry products have been shown to give light-absorbing and high molecular weight oligomeric species, which increase the SOA mass production and alter the direct and indirect effect of aerosols. In this paper, the aerosol chemistry of small α-dicarbonyl compounds with amines is investigated and the associated optical properties are measured using spectroscopic techniques. The differences between primary, secondary and tertiary amines with glyoxal and methylglyoxal are evaluated in terms of SOA browning efficiency. Atmospheric implications of our present work for understanding the formation of light-absorbing SOA will be presented, particularly in terms of the product distribution of light-absorbing SOA formed by aqueous phase

  19. Relationship between oxidation level and optical properties of secondary organic aerosol.

    PubMed

    Lambe, Andrew T; Cappa, Christopher D; Massoli, Paola; Onasch, Timothy B; Forestieri, Sara D; Martin, Alexander T; Cummings, Molly J; Croasdale, David R; Brune, William H; Worsnop, Douglas R; Davidovits, Paul

    2013-06-18

    Brown carbon (BrC), which may include secondary organic aerosol (SOA), can be a significant climate-forcing agent via its optical absorption properties. However, the overall contribution of SOA to BrC remains poorly understood. Here, correlations between oxidation level and optical properties of SOA are examined. SOA was generated in a flow reactor in the absence of NOx by OH oxidation of gas-phase precursors used as surrogates for anthropogenic (naphthalene, tricyclo[5.2.1.0(2,6)]decane), biomass burning (guaiacol), and biogenic (α-pinene) emissions. SOA chemical composition was characterized with a time-of-flight aerosol mass spectrometer. SOA mass-specific absorption cross sections (MAC) and refractive indices were calculated from real-time cavity ring-down photoacoustic spectrometry measurements at 405 and 532 nm and from UV-vis spectrometry measurements of methanol extracts of filter-collected particles (300 to 600 nm). At 405 nm, SOA MAC values and imaginary refractive indices increased with increasing oxidation level and decreased with increasing wavelength, leading to negligible absorption at 532 nm. Real refractive indices of SOA decreased with increasing oxidation level. Comparison with literature studies suggests that under typical polluted conditions the effect of NOx on SOA absorption is small. SOA may contribute significantly to atmospheric BrC, with the magnitude dependent on both precursor type and oxidation level. PMID:23701291

  20. Observed correlations between aerosol and cloud properties in an Indian Ocean trade cumulus regime

    DOE PAGES

    Pistone, Kristina; Praveen, Puppala S.; Thomas, Rick M.; Ramanathan, Veerabhadran; Wilcox, Eric M.; Bender, Frida A.-M.

    2016-04-27

    There are many contributing factors which determine the micro- and macrophysical properties of clouds, including atmospheric vertical structure, dominant meteorological conditions, and aerosol concentration, all of which may be coupled to one another. In the quest to determine aerosol effects on clouds, these potential relationships must be understood. Here we describe several observed correlations between aerosol conditions and cloud and atmospheric properties in the Indian Ocean winter monsoon season.In the CARDEX (Cloud, Aerosol, Radiative forcing, Dynamics EXperiment) field campaign conducted in February and March 2012 in the northern Indian Ocean, continuous measurements were made of atmospheric precipitable water vapor (PWV)more » and the liquid water path (LWP) of trade cumulus clouds, concurrent with measurements of water vapor flux, cloud and aerosol vertical profiles, meteorological data, and surface and total-column aerosol from instrumentation at a ground observatory and on small unmanned aircraft. We present observations which indicate a positive correlation between aerosol and cloud LWP only when considering cases with low atmospheric water vapor (PWV < 40 kg m–2), a criterion which acts to filter the data to control for the natural meteorological variability in the region.We then use the aircraft and ground-based measurements to explore possible mechanisms behind this observed aerosol–LWP correlation. The increase in cloud liquid water is found to coincide with a lowering of the cloud base, which is itself attributable to increased boundary layer humidity in polluted conditions. High pollution is found to correlate with both higher temperatures and higher humidity measured throughout the boundary layer. A large-scale analysis, using satellite observations and meteorological reanalysis, corroborates these covariations: high-pollution cases are shown to originate as a highly polluted boundary layer air mass approaching the observatory from a

  1. Optical Properties of Atmospheric Aerosol in Maritime Environments.

    NASA Astrophysics Data System (ADS)

    Smirnov, Alexander; Holben, Brent N.; Kaufman, Yoram J.; Dubovik, Oleg; Eck, Thomas F.; Slutsker, Ilya; Pietras, Christophe; Halthore, Rangasayi N.

    2002-02-01

    Systematic characterization of aerosol over the oceans is needed to understand the aerosol effect on climate and on transport of pollutants between continents. Reported are the results of a comprehensive optical and physical characterization of ambient aerosol in five key island locations of the Aerosol Robotic Network (AERONET) of sun and sky radiometers, spanning over 2-5 yr. The results are compared with aerosol optical depths and size distributions reported in the literature over the last 30 yr. Aerosol found over the tropical Pacific Ocean (at three sites between 20°S and 20°N) still resembles mostly clean background conditions dominated by maritime aerosol. The optical thickness is remarkably stable with mean value of a(500 nm) = 0.07, mode value at am = 0.06, and standard deviation of 0.02-0.05. The average Ångström exponent range, from 0.3 to 0.7, characterizes the wavelength dependence of the optical thickness. Over the tropical to subtropical Atlantic (two stations at 7°S and 32°N) the optical thickness is significantly higher: a(500 nm) = 0.14 and am = 0.10 due to the frequent presence of dust, smoke, and urban-industrial aerosol. For both oceans the atmospheric column aerosol is characterized by a bimodal lognormal size distribution with a fine mode at effective radius Reff = 0.11 ± 0.01 m and coarse mode at Reff = 2.1 ± 0.3 m. A review of the published 150 historical ship measurements from the last three decades shows that am was around 0.07 to 0.12 in general agreement with the present finding. The information should be useful as a test bed for aerosol global models and aerosol representation in global climate models. With global human population expansion and industrialization, these measurements can serve in the twenty-first century as a basis to assess decadal changes in the aerosol concentration, properties, and radiative forcing of climate.

  2. Aerosol Properties over the Eastern North Pacific based on Measurements from the MAGIC Field Campaign

    NASA Astrophysics Data System (ADS)

    Lewis, E. R.; Senum, G.; Springston, S. R.; Kuang, C.

    2015-12-01

    The MAGIC field campaign, funded and operated by the ARM (Atmospheric Radiation Measurement) Climate Research Facility of the US Department of Energy, occurred between September 2012 and October, 2013 aboard the Horizon Lines cargo container ship Spirit making regular trips between Los Angeles, CA and Honolulu, HI. Along this route, which lies very near the GPCI (GCSS Pacific Cross-section Intercomparison) transect, the predominant cloud regime changes from stratocumulus near the California coast to trade-wind cumulus near Hawaii. The transition between these two regimes is poorly understood and not accurately represented in models. The goal of MAGIC was to acquire statistic of this transition and thus improve its representation in models by making repeated transects through this region and measuring properties of clouds and precipitation, aerosols, radiation, and atmospheric structure. To achieve these goals, the Second ARM Mobile Facility (AMF2) was deployed on the Horizon Spirit as it ran its regular route between Los Angeles and Honolulu. AMF2 consists of three 20-foot SeaTainers and includes three radars and other instruments to measure properties of clouds and precipitation; the Aerosol Observing System (AOS), which has a suite of instruments to measure properties of aerosols; and other instruments to measure radiation, meteorological quantities, and sea surface temperature. Two technicians accompanied the AMF2, and scientists rode the ship as observers. MAGIC made nearly 20 round trips between Los Angeles and Honolulu (and thus nearly 40 excursions through the stratocumulus-to-cumulus transition) and spent 200 days at sea, collecting an unprecedented data set. Aerosol properties measured with the AOS include number concentration and size distribution, CCN activity, hygroscopic growth, and light-scattering and absorption. Additionally, more than one hundred filter samples were collected. Aerosol properties and their spatial and temporal behavior are discussed

  3. Differences in aerosol absorption Ångström exponents between correction algorithms for a particle soot absorption photometer measured on the South African Highveld

    NASA Astrophysics Data System (ADS)

    Backman, J.; Virkkula, A.; Vakkari, V.; Beukes, J. P.; Van Zyl, P. G.; Josipovic, M.; Piketh, S.; Tiitta, P.; Chiloane, K.; Petäjä, T.; Kulmala, M.; Laakso, L.

    2014-12-01

    Absorption Ångström exponents (AAEs) calculated from filter-based absorption measurements are often used to give information on the origin of the ambient aerosol, for example, to distinguish between urban pollution and biomass burning aerosol. Filter-based absorption measurements are widely used and are common at aerosol monitoring stations globally. Several correction algorithms are used to account for artefacts associated with filter-based absorption techniques. These algorithms are of profound importance when determining the absolute amount of absorption by the aerosol. However, this study shows that there are substantial differences between the AAEs calculated from these corrections. Depending on the used correction, AAEs can change by as much as 46%. The study also highlights that the difference between AAEs calculated using different corrections can lead to conflicting conclusions on the type of aerosol when using the same data set. The AAE ranged between 1.17 for non-corrected data to 1.96 for the correction that gave the greatest values. Furthermore, the study implies that the AAEs reported for a site depend on at which filter transmittance the filter is changed. In this work, the AAEs were calculated from data measured with a three-wavelength particle soot absorption photometer (PSAP) at Elandsfontein on the South African Highveld for 23 months. The sample air of the PSAP was diluted to prolong filter change intervals, by a factor of 15. The correlation coefficient between the dilution-corrected PSAP and a non-diluted Multi-Angle Absorption Photometer (MAAP) was 0.9. Thus, the study also shows that the applicability of the PSAP can be extended to remote sites that are not often visited or suffer from high levels of pollution.

  4. Optical and Physicochemical Properties of Brown Carbon Aerosol: Light Scattering, FTIR Extinction Spectroscopy, and Hygroscopic Growth.

    PubMed

    Tang, Mingjin; Alexander, Jennifer M; Kwon, Deokhyeon; Estillore, Armando D; Laskina, Olga; Young, Mark A; Kleiber, Paul D; Grassian, Vicki H

    2016-06-23

    A great deal of attention has been paid to brown carbon aerosol in the troposphere because it can both scatter and absorb solar radiation, thus affecting the Earth's climate. However, knowledge of the optical and chemical properties of brown carbon aerosol is still limited. In this study, we have investigated different aspects of the optical properties of brown carbon aerosol that have not been previously explored. These properties include extinction spectroscopy in the mid-infrared region and light scattering at two different visible wavelengths, 532 and 402 nm. A proxy for atmospheric brown carbon aerosol was formed from the aqueous reaction of ammonium sulfate with methylglyoxal. The different optical properties were measured as a function of reaction time for a period of up to 19 days. UV/vis absorption experiments of bulk solutions showed that the optical absorption of aqueous brown carbon solution significantly increases as a function of reaction time in the spectral range from 200 to 700 nm. The analysis of the light scattering data, however, showed no significant differences between ammonium sulfate and brown carbon aerosol particles in the measured scattering phase functions, linear polarization profiles, or the derived real parts of the refractive indices at either 532 or 402 nm, even for the longest reaction times with greatest visible extinction. The light scattering experiments are relatively insensitive to the imaginary part of the refractive index, and it was only possible to place an upper limit of k ≤ 0.01 on the imaginary index values. These results suggest that after the reaction with methylglyoxal the single scattering albedo of ammonium sulfate aerosol is significantly reduced but that the light scattering properties including the scattering asymmetry parameter, which is a measure of the relative amount of forward-to-backward scattering, remain essentially unchanged from that of unprocessed ammonium sulfate. The optical extinction properties

  5. Optical and Physicochemical Properties of Brown Carbon Aerosol: Light Scattering, FTIR Extinction Spectroscopy, and Hygroscopic Growth.

    PubMed

    Tang, Mingjin; Alexander, Jennifer M; Kwon, Deokhyeon; Estillore, Armando D; Laskina, Olga; Young, Mark A; Kleiber, Paul D; Grassian, Vicki H

    2016-06-23

    A great deal of attention has been paid to brown carbon aerosol in the troposphere because it can both scatter and absorb solar radiation, thus affecting the Earth's climate. However, knowledge of the optical and chemical properties of brown carbon aerosol is still limited. In this study, we have investigated different aspects of the optical properties of brown carbon aerosol that have not been previously explored. These properties include extinction spectroscopy in the mid-infrared region and light scattering at two different visible wavelengths, 532 and 402 nm. A proxy for atmospheric brown carbon aerosol was formed from the aqueous reaction of ammonium sulfate with methylglyoxal. The different optical properties were measured as a function of reaction time for a period of up to 19 days. UV/vis absorption experiments of bulk solutions showed that the optical absorption of aqueous brown carbon solution significantly increases as a function of reaction time in the spectral range from 200 to 700 nm. The analysis of the light scattering data, however, showed no significant differences between ammonium sulfate and brown carbon aerosol particles in the measured scattering phase functions, linear polarization profiles, or the derived real parts of the refractive indices at either 532 or 402 nm, even for the longest reaction times with greatest visible extinction. The light scattering experiments are relatively insensitive to the imaginary part of the refractive index, and it was only possible to place an upper limit of k ≤ 0.01 on the imaginary index values. These results suggest that after the reaction with methylglyoxal the single scattering albedo of ammonium sulfate aerosol is significantly reduced but that the light scattering properties including the scattering asymmetry parameter, which is a measure of the relative amount of forward-to-backward scattering, remain essentially unchanged from that of unprocessed ammonium sulfate. The optical extinction properties

  6. Retrieval of aerosol optical properties over land using PMAp

    NASA Astrophysics Data System (ADS)

    Grzegorski, Michael; Munro, Rosemary; Lang, Ruediger; Poli, Gabriele; Holdak, Andriy

    2015-04-01

    The retrieval of aerosol optical properties is an important task for industry and climate forecasting. An ideal instrument should include observations with moderate spectral and high spatial resolutions for a wide range of wavelengths (from the UV to the TIR), measurements of the polarization state at different wavelengths and measurements of the same scene for different observation geometries. As such an ideal instrument is currently unavailable the usage of different instruments on one satellite platform is an alternative choice. Since February 2014, the Polar Multi sensor Aerosol product (PMAp) is delivered as operational GOME product to our customers. The algorithms retrieve aerosol optical properties over ocean (AOD, volcanic ash, aerosol type) using a multi-sensor approach (GOME, AVHRR, IASI). The next releases of PMAp will provide an extended set of aerosol and cloud properties which include AOD over land and an improved volcanic ash retrieval combining AVHRR and IASI. This presentation gives an overview on the existing product and the prototypes in development. The major focus is the discussion of the AOD retrieval over land implemented in the upcoming PMAp2 release. In addition, the results of our current validation studies (e.g. comparisons to AERONET, other satellite platforms and model data) are shown.

  7. Light absorption by airborne aerosols: comparison of integrating plate and spectrophone techniques.

    PubMed

    Szkarlat, A C; Japar, S M

    1981-04-01

    An excellent correlation between the integrating plate (IP) and the photoacoustic methods for measuring aerosol light absorption has been found for airborne graphitic carbon in diesel vehicle exhaust. However, the regression coefficient depends on the orientation of the Teflon membrane filter during the IP analysis. With the collected particulates between the filter and the integrating plate, the IP response is 1.85 times that for the filter reversed. In either case the response ratio of the IP method to the photoacoustic method is >1.0, i.e., 2.43 vs 1.30. The IP calibration is also probably dependent on the nature of the filter medium. PMID:20309278

  8. Optical Properties of Wintertime Aerosols from Residential Wood Burning in Fresno, CA: Results from DISCOVER-AQ 2013.

    PubMed

    Zhang, Xiaolu; Kim, Hwajin; Parworth, Caroline L; Young, Dominique E; Zhang, Qi; Metcalf, Andrew R; Cappa, Christopher D

    2016-02-16

    The optical properties, composition and sources of the wintertime aerosols in the San Joaquin Valley (SJV) were characterized through measurements made in Fresno, CA during the 2013 DISCOVER-AQ campaign. PM2.5 extinction and absorption coefficients were measured at 405, 532, and 870 nm along with refractory black carbon (rBC) size distributions and concentrations. BC absorption enhancements (Eabs) were measured using two methods, a thermodenuder and mass absorption coefficient method, which agreed well. Relatively large diurnal variations in the Eabs at 405 nm were observed, likely reflecting substantial nighttime emissions of wood burning organic aerosols (OA) from local residential heating. Comparably small diurnal variations and absolute nighttime values of Eabs were observed at the other wavelengths, suggesting limited mixing-driven enhancement. Positive matrix factorization analysis of OA mass spectra from an aerosol mass spectrometer resolved two types of biomass burning OA, which appeared to have different chemical composition and absorptivity. Brown carbon (BrC) absorption was estimated to contribute up to 30% to the total absorption at 405 nm at night but was negligible (<10%) during the day. Quantitative understanding of retrieved BrC optical properties could be improved with more explicit knowledge of the BC mixing state and the distribution of coating thicknesses. PMID:26771892

  9. The optical, chemical, and physical properties of aerosols and gases emitted by the laboratory combustion of wildland fuels

    NASA Astrophysics Data System (ADS)

    McMeeking, Gavin R.

    ignored, the light absorption by organic carbon can cause errors in predicted surface ultraviolet and visible radiation fluxes and photochemical photolysis rates in regions affected by biomass burning emissions. The dependence of spectral aerosol optical properties on combustion conditions means that fire behavior must be accurately assessed and predicted to ensure accurate emissions inventories and estimates of biomass burning atmospheric impacts.

  10. Evolution of biomass burning aerosol over the Amazon: airborne measurements of aerosol chemical composition, microphysical properties, mixing state and optical properties during SAMBBA

    NASA Astrophysics Data System (ADS)

    Morgan, W.; Allan, J. D.; Flynn, M.; Darbyshire, E.; Hodgson, A.; Liu, D.; O'Shea, S.; Bauguitte, S.; Szpek, K.; Johnson, B.; Haywood, J.; Longo, K.; Artaxo, P.; Coe, H.

    2013-12-01

    Biomass burning represents one of the largest sources of particulate matter to the atmosphere, resulting in a significant perturbation to the Earth's radiative balance coupled with serious impacts on public health. On regional scales, the impacts are substantial, particularly in areas such as the Amazon Basin where large, intense and frequent burning occurs on an annual basis for several months. Absorption by atmospheric aerosols is underestimated by models over South America, which points to significant uncertainties relating to Black Carbon (BC) aerosol properties. Initial results from the South American Biomass Burning Analysis (SAMBBA) field experiment, which took place during September and October 2012 over Brazil on-board the UK Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 research aircraft, are presented here. Aerosol chemical composition was measured by an Aerodyne Aerosol Mass Spectrometer (AMS) and a DMT Single Particle Soot Photometer (SP2). The physical, chemical and optical properties of the aerosols across the region will be characterized in order to establish the impact of biomass burning on regional air quality, weather and climate. The aircraft sampled a range of conditions including sampling of pristine Rainforest, fresh biomass burning plumes, regional haze and elevated biomass burning layers within the free troposphere. The aircraft sampled biomass burning aerosol across the southern Amazon in the states of Rondonia and Mato Grosso, as well as in a Cerrado (Savannah-like) region in Tocantins state. This presented a range of fire conditions, in terms of their number, intensity, vegetation-type and their combustion efficiencies. Near-source sampling of fires in Rainforest environments suggested that smouldering combustion dominated, while flaming combustion dominated in the Cerrado. This led to significant differences in aerosol chemical composition, particularly in terms of the BC content, with BC being enhanced in the Cerrado

  11. Absorption and fluorescence properties of fluorescein

    NASA Astrophysics Data System (ADS)

    Sjöback, Robert; Nygren, Jan; Kubista, Mikael

    1995-06-01

    We have characterized the protolytic equilibria of fluorescein and determined the spectroscopic properties of its protolytic forms. The protolytic constants relating the chemical activities (which at low ionic strength equal concentrations) of the cation, neutral form, anion and dianion are p K1 = 2.08, p K2 = 4.31, and p K3 = 6.43. All forms have rather high molar absorptivities being ɛ437FH 3 1 = 53 000, ɛ434FH 2 = 11 000, ɛ453FH- = 29 000 ( ɛ472FH = 29 000) and ɛ490F 2 = 76 900 M -1 cm -1 for the cation, neutral form, anion and dianion, respectively. The dianion has the most intense fluorescence with a quantum yield of 0.93 but also the anion shows considerable fluorescence with a quantum yield of 0.37. The neutral and cationic species are upon excitation converted into the anion and fluoresce with quantum yields of about 0.30 and 0.18, respectively.

  12. Effect of CALIPSO Cloud Aerosol Discrimination (CAD) Confidence Levels on Observations of Aerosol Properties near Clouds

    NASA Technical Reports Server (NTRS)

    Yang, Weidong; Marshak, Alexander; Varnai, Tamas; Liu, Zhaoyan

    2012-01-01

    CALIPSO aerosol backscatter enhancement in the transition zone between clouds and clear sky areas is revisited with particular attention to effects of data selection based on the confidence level of cloud-aerosol discrimination (CAD). The results show that backscatter behavior in the transition zone strongly depends on the CAD confidence level. Higher confidence level data has a flatter backscatter far away from clouds and a much sharper increase near clouds (within 4 km), thus a smaller transition zone. For high confidence level data it is shown that the overall backscatter enhancement is more pronounced for small clear-air segments and horizontally larger clouds. The results suggest that data selection based on CAD reduces the possible effects of cloud contamination when studying aerosol properties in the vicinity of clouds.

  13. Synergistic analyses of optical and microphysical properties of agricultural crop residue burning aerosols over the Indo-Gangetic Basin (IGB)

    NASA Astrophysics Data System (ADS)

    Mishra, Amit Kumar; Shibata, Takashi

    2012-09-01

    Agriculture crop residue burning is one of the important sources of trace gas emissions and aerosol loading over the Indo-Gangetic Basin (IGB). The present study deals with the spatial variability including the vertical structure of optical and microphysical properties of aerosols, during the crop residue burning season (October and November) of 2009 over the IGB. Increased number of fire counts observed by MODIS (MODerate resolution Imaging Spectroradiometer) that is associated with high aerosol optical depth (MODIS-AOD > 0.7) and enhanced tropospheric columnar NO2 concentrations observed by OMI (Ozone Monitoring Instrument), suggests agriculture crop residue burning as a main source of aerosol loading over the IGB during October and November. PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Science coupled with Observations from a Lidar) observations show an increase in fine mode AOD (at 865 nm) from October (0.1-0.2) to November (0.2-0.3) over the IGB, which is well corroborated with MODIS observations. CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) data shows the elevated aerosol plume (4.0-4.5 km) over the north-west IGB (associated with burning activities) that could have been caused by positive buoyancy through pyro-convection. However, large concentrations of aerosol were found below 1.0 km altitude. The averaged vertical structure of crop residue burning aerosols shows an exponential decrease with altitude (mean scale height ˜1.44 ± 0.20 km). Aerosol optical and microphysical properties coupled with backward air trajectories analyses at Kanpur indicated regional transport of biomass burning aerosols in a downwind direction from north-west IGB to south-east IGB. Aerosol classification, using AERONET (AErosol RObotic NETwork)-derived absorption properties coupled with size parameter (2006-2010) showed clear seasonal dependency of aerosol types which revealed the presence of biomass burning aerosols only during the crop

  14. Variability in morphology, hygroscopicity, and optical properties of soot aerosols during atmospheric processing.

    PubMed

    Zhang, Renyi; Khalizov, Alexei F; Pagels, Joakim; Zhang, Dan; Xue, Huaxin; McMurry, Peter H

    2008-07-29

    The atmospheric effects of soot aerosols include interference with radiative transfer, visibility impairment, and alteration of cloud formation and are highly sensitive to the manner by which soot is internally mixed with other aerosol constituents. We present experimental studies to show that soot particles acquire a large mass fraction of sulfuric acid during atmospheric aging, considerably altering their properties. Soot particles exposed to subsaturated sulfuric acid vapor exhibit a marked change in morphology, characterized by a decreased mobility-based diameter but an increased fractal dimension and effective density. These particles experience large hygroscopic size and mass growth at subsaturated conditions (<90% relative humidity) and act efficiently as cloud-condensation nuclei. Coating with sulfuric acid and subsequent hygroscopic growth enhance the optical properties of soot aerosols, increasing scattering by approximately 10-fold and absorption by nearly 2-fold at 80% relative humidity relative to fresh particles. In addition, condensation of sulfuric acid is shown to occur at a similar rate on ambient aerosols of various types of a given mobility size, regardless of their chemical compositions and microphysical structures. Representing an important mechanism of atmospheric aging, internal mixing of soot with sulfuric acid has profound implications on visibility, human health, and direct and indirect climate forcing.

  15. Synthesis of information on aerosol optical properties

    NASA Astrophysics Data System (ADS)

    Liu, Hongqing; Pinker, R. T.; Chin, M.; Holben, B.; Remer, L.

    2008-04-01

    In a previous study (Liu et al., 2005) obtained are global scale estimates of aerosol optical depth at 0.55 μm based on spatial and temporal variation patterns from models and satellite observations, regulated by the Aerosol Robotic Network (AERONET) measurements. In this study an approach is developed to obtain information on global distribution of the single scattering albedo (ω0), the asymmetry parameter (g), and the normalized extinction coefficient over shortwave (SW) spectrum. Since space observations of ω0 are in early stages of development and none are available for g, first an approach was developed to infer them from relevant information from the Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model, Moderate Resolution Imaging Spectroradiometer (MODIS) and AERONET retrievals. The single scattering albedo is generated by extending GOCART ω0 at 0.55 μm to the entire SW spectrum using spectral dependence derived from AERONET retrievals. The asymmetry parameter over the solar spectrum is derived from the MODIS Ångström wavelength exponent, utilizing a relationship based on AERONET almucantar observations. The normalized extinction coefficient is estimated from the MODIS Ångström wavelength exponent. The methodology was implemented as a "proof of concept" with one year of data. The approach described here is a step in preparedness for utilizing information from new observing systems (e.g., MISR, A-Train constellation) when available. The impact of the newly derived information on the quality of satellite based estimates of surface radiative fluxes was evaluated and is presented by Liu and Pinker (2008).

  16. Simultaneous retrieval of aerosol and surface optical properties from combined airborne- and ground-based direct and diffuse radiometric measurements

    NASA Astrophysics Data System (ADS)

    Gatebe, C. K.; Dubovik, O.; King, M. D.; Sinyuk, A.

    2009-12-01

    This paper presents a new method for simultaneously retrieving aerosol and surface reflectance properties from combined airborne and ground-based direct and diffuse radiometric measurements. The method is based on the standard Aerosol Robotic Network (AERONET) method for retrieving aerosol size distribution, complex index of refraction, and single scattering albedo, but modified to retrieve aerosol properties in two layers, below and above the aircraft, and parameters on surface optical properties from combined datasets (Cloud Absorption Radiometer, CAR, and AERONET data). A key advantage of this method is the inversion of all available spectral and angular data at the same time, while accounting for the influence of noise in the inversion procedure using statistical optimization. The wide spectral (0.34-2.30 μm) and angular range (180°) of the CAR instrument, combined with observations from an AERONET sunphotometer, provide sufficient measurement constraints for characterizing aerosol and surface properties with minimal assumptions. The robustness of the method was tested on observations made during four different field campaigns: (a) the Southern African Regional Science Initiative 2000 over Mongu, Zambia, (b) the Intercontinental Transport Experiment-Phase B over Mexico City, Mexico (c) Cloud and Land Surface Interaction Campaign over the Atmospheric Radiation Measurement (ARM) Central Facility, Oklahoma, USA, and (d) the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) over Elson Lagoon in Barrow, Alaska, USA. The four areas are dominated by different surface characteristics and aerosol types, and therefore provide good test cases for the new inversion method.

  17. Simultaneous Retrieval of Aerosol and Surface Optical Properties from Combined Airborne- and Ground-Based Direct and Diffuse Radiometric Measurements

    NASA Technical Reports Server (NTRS)

    Gatebe, C. K.; Dubovik, O.; King, M. D.; Sinyuk, A.

    2010-01-01

    This paper presents a new method for simultaneously retrieving aerosol and surface reflectance properties from combined airborne and ground-based direct and diffuse radiometric measurements. The method is based on the standard Aerosol Robotic Network (AERONET) method for retrieving aerosol size distribution, complex index of refraction, and single scattering albedo, but modified to retrieve aerosol properties in two layers, below and above the aircraft, and parameters on surface optical properties from combined datasets (Cloud Absorption Radiometer (CAR) and AERONET data). A key advantage of this method is the inversion of all available spectral and angular data at the same time, while accounting for the influence of noise in the inversion procedure using statistical optimization. The wide spectral (0.34-2.30 m) and angular range (180 ) of the CAR instrument, combined with observations from an AERONET sunphotometer, provide sufficient measurement constraints for characterizing aerosol and surface properties with minimal assumptions. The robustness of the method was tested on observations made during four different field campaigns: (a) the Southern African Regional Science Initiative 2000 over Mongu, Zambia, (b) the Intercontinental Transport Experiment-Phase B over Mexico City, Mexico (c) Cloud and Land Surface Interaction Campaign over the Atmospheric Radiation Measurement (ARM) Central Facility, Oklahoma, USA, and (d) the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) over Elson Lagoon in Barrow, Alaska, USA. The four areas are dominated by different surface characteristics and aerosol types, and therefore provide good test cases for the new inversion method.

  18. Properties of Stratospheric Aerosol Estimated from HALOE Data

    NASA Technical Reports Server (NTRS)

    Lee, Kwang-Mog; Park, Jae H.; Massie, Steven T.; Choi, Wookap

    2001-01-01

    Extinction coefficients for stratospheric aerosols at 8 HALOE (HALogen Occultation Experiment) wavelengths are determined by comparing transmittances data for two adjacent solar occultation measurements, where one limb path is loaded with aerosols but the other path is free of aerosols. These extinction coefficients are used to infer the aerosol properties such as composition and size distribution parameters. Mie theory has been used to calculate the extinction coefficients, and a nonlinear least square method is applied to determine the aerosol properties. Sixteen cases are selected for the retrieval in southern hemisphere at latitudes from 21 to 48 deg S for the period of 29 Mar - 31 May 1992. Retrieved size width ranges from 1.1 to 1.5 and radius ranges from 0.25 to 0.45 micrometers. These size parameters are within the ranges of in situ measurements at Laramie, Wyoming. Retrieved weight percent of H2SO4 is larger than the equilibrium value by about 5 to approximately 10 weight percent, similar to the results for northern hemisphere at latitudes 20 to 55 deg N for the period from Nov 1991 to Feb. 1992.

  19. Reduction of Aerosol Absorption in Beijing Since 2007 from MODIS and AERONET

    NASA Technical Reports Server (NTRS)

    Lyapustin, A.; Smirnov, A.; Holben, B.; Chin, M.; Streets, D. G.; Lu, Z.; Kahn, R.; Slutsker, I.; Laszlo, I.; Kondragunta, S.; Tanre, D.; Dubovik, O.; Goloub, P.; Chen, H.-B.; Sinyuk, A.; Wang, Y.; Korkin, S.

    2011-01-01

    An analysis of the time series of MODIS-based and AERONET aerosol records over Beijing reveals two distinct periods, before and after 2007. The MODIS data from both the Terra and Aqua satellites were processed with the new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm. A comparison of MAIAC and AERONET AOT shows that whereas MAIAC consistently underestimated peak AOT values by 10-20% in the prior period, the bias mostly disappears after mid- 2007. Independent analysis of the AERONET dataset reveals little or no change in the effective radii of the fine and coarse fractions and of the Angstrom exponent. At the same time, it shows an increasing trend in the single scattering albedo, by 0.02 in 9 years. As MAIAC was using the same aerosol model for the entire 2000-2010 period, the decrease in AOT bias after 2007 can be explained only by a corresponding decrease of aerosol absorption caused by a reduction in local black carbon emissions. The observed changes correlate in time with the Chinese government's broad measures to improve air quality in Beijing during preparations for the Summer Olympics of 2008.

  20. Reduction of Aerosol Absorption in Beijing Since 2007 from MODIS and AERONET

    NASA Technical Reports Server (NTRS)

    Lyapustin, A.; Smirnov, A.; Holben, B.; Chin, M.; Streets, D. G.; Lu, Z.; Kahn, R.; Slutsker, I.; Laszlo, I.; Kondragunta, S.; Tanre, D.; Dubovik, O.; Goloub, P.; Chen, H.-B.; Sinyuk, A.; Wang, Y.; Korkin, S.

    2011-01-01

    An analysis of the time series of MODIS-based and AERONET aerosol records over Beijing reveals two distinct periods, before and after 2007. The MODIS data from both the Terra and Aqua satellites were processed with the new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm. A comparison of MAIAC and AERONET AOT shows that whereas MAIAC consistently underestimated peak AOT values by 10-20% in the prior period, the bias mostly disappears after mid-2007. Independent analysis of the AERONET dataset reveals little or no change in the effective radii of the fine and coarse fractions and of the Angstrom exponent. At the same time, it shows an increasing trend in the single scattering albedo, by approx.0.02 in 9 years. As MAIAC was using the same aerosol model for the entire 2000-2010 period, the decrease in AOT bias after 2007 can be explained only by a corresponding decrease of aerosol absorption caused by a reduction in local black carbon emissions. The observed changes correlate in time with the Chinese government's broad measures to improve air quality in Beijing during preparations for the Summer Olympics of 2008.

  1. Reduction of aerosol absorption in Beijing since 2007 from MODIS and AERONET

    NASA Astrophysics Data System (ADS)

    Lyapustin, A.; Smirnov, A.; Holben, B.; Chin, M.; Streets, D. G.; Lu, Z.; Kahn, R.; Slutsker, I.; Laszlo, I.; Kondragunta, S.; Tanré, D.; Dubovik, O.; Goloub, P.; Chen, H.-B.; Sinyuk, A.; Wang, Y.; Korkin, S.

    2011-05-01

    An analysis of the time series of MODIS-based and AERONET aerosol records over Beijing reveals two distinct periods, before and after 2007. The MODIS data from both the Terra and Aqua satellites were processed with the new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm. A comparison of MAIAC and AERONET AOT shows that whereas MAIAC consistently underestimated peak AOT values by 10-20% in the prior period, the bias mostly disappears after mid-2007. Independent analysis of the AERONET dataset reveals little or no change in the effective radii of the fine and coarse fractions and of the Ångström exponent. At the same time, it shows an increasing trend in the single scattering albedo, by ˜0.02 in 9 years. As MAIAC was using the same aerosol model for the entire 2000-2010 period, the decrease in AOT bias after 2007 can be explained only by a corresponding decrease of aerosol absorption caused by a reduction in local black carbon emissions. The observed changes correlate in time with the Chinese government's broad measures to improve air quality in Beijing during preparations for the Summer Olympics of 2008.

  2. Composition and physical properties of the Asian Tropopause Aerosol Layer and the North American Tropospheric Aerosol Layer

    PubMed Central

    Yu, Pengfei; Toon, Owen B; Neely, Ryan R; Martinsson, Bengt G; Brenninkmeijer, Carl A M

    2015-01-01

    Recent studies revealed layers of enhanced aerosol scattering in the upper troposphere and lower stratosphere over Asia (Asian Tropopause Aerosol Layer (ATAL)) and North America (North American Tropospheric Aerosol Layer (NATAL)). We use a sectional aerosol model (Community Aerosol and Radiation Model for Atmospheres (CARMA)) coupled with the Community Earth System Model version 1 (CESM1) to explore the composition and optical properties of these aerosol layers. The observed aerosol extinction enhancement is reproduced by CESM1/CARMA. Both model and observations indicate a strong gradient of the sulfur-to-carbon ratio from Europe to the Asia on constant pressure surfaces. We found that the ATAL is mostly composed of sulfates, surface-emitted organics, and secondary organics; the NATAL is mostly composed of sulfates and secondary organics. The model also suggests that emission increases in Asia between 2000 and 2010 led to an increase of aerosol optical depth of the ATAL by 0.002 on average which is consistent with observations. Key Points The Asian Tropopause Aerosol Layer is composed of sulfate, primary organics, and secondary organics The North American Tropospheric Aerosol Layer is mostly composed of sulfate and secondary organics Aerosol Optical Depth of Asian Tropopause Aerosol Layer increases by 0.002 from 2000 to 2010 PMID:26709320

  3. Physical and Chemical Properties of Aerosols at the Tropical Coastal Site, Trivandrum

    NASA Astrophysics Data System (ADS)

    George, Susan K.; Nair, Prabha R.; Parameswaran, Krishnaswamy; Jacob, Salu; Abraham, Annamma; Abhilash, K. S.

    The influence of tropospheric aerosols on the regional climate is fairly well accepted though there exists large uncertainties in assessing its exact magnitude. This is mainly due to the fact that the aerosol properties are highly variable at short spatial and temporal extents and the information available is rather limited. To overcome these deficiency it is highly essential to gather and analyse long term data covering different seasons over varying climatic regimes. Trivandrum (8.55o N, 77o E), a tropical coastal site situated near the southern tip of Indian Peninsula, is a location where systematic monitoring of different aerosol parameters are being carried out since last two decades. With progressing time new techniques and instruments are also being incorporated. This paper presents the results from the observations on aerosols carried out during the period 2003 to 2005 at this location. Different aerosol properties such as total mass concentration, number density, size distribution, optical depth, chemical composition, etc. are studied systematically during this period. A High Volume Sampler (for measuring total mass loading), Aerosol Spectrometer (for measuring size segregated number density from which size distribution can be derived), and Microtops Sunphotometer (which measures optical depth at 1020 nm) are used to study the physical/optical properties of aerosols. The chemical composition of atmospheric aerosols is examined employing Ion Chromatography, Atomic Absorption Spectroscopy and Inductively Couple Plasma - Atomic Emission Spectroscopy. The mean mass concentration of aerosols observed at this site is 54 µg m-3 , which varies by ±19 µg m-3 depending on season and prevailing meteorology. The aerosol number density is 108 particles/m3 . The mass loading at this location is significantly low compared to the northern parts of India as well as the national ambient air quality standards indicating that the environment is relatively less polluted as

  4. Atmospheric correction of ocean color imagery: use of the junge power-law aerosol size distribution with variable refractive index to handle aerosol absorption.

    PubMed

    Chomko, R M; Gordon, H R

    1998-08-20

    When strongly absorbing aerosols are present in the atmosphere, the usual two-step procedure of processing ocean color data-(1) atmospheric correction to provide the water-leaving reflectance (rho(w)), followed by (2) relating rho(w) to the water constituents-fails and simultaneous estimation of the ocean and aerosol optical properties is necessary. We explore the efficacy of using a simple model of the aerosol-a Junge power-law size distribution consisting of homogeneous spheres with arbitrary refractive index-in a nonlinear optimization procedure for estimating the relevant oceanic and atmospheric parameters for case 1 waters. Using simulated test data generated from more realistic aerosol size distributions (sums of log-normally distributed components with different compositions), we show that the ocean's pigment concentration (C) can be retrieved with good accuracy in the presence of weakly or strongly absorbing aerosols. However, because of significant differences in the scattering phase functions for the test and power-law distributions, large error is possible in the estimate of the aerosol optical thickness. The positive result for C suggests that the detailed shape of the aerosol-scattering phase function is not relevant to the atmospheric correction of ocean color sensors. The relevant parameters are the aerosol single-scattering albedo and the spectral variation of the aerosol optical depth. We argue that the assumption of aerosol sphericity should not restrict the validity of the algorithm and suggest an avenue for including colored aerosols, e.g., wind-blown dust, in the procedure. A significant advantage of the new approach is that realistic multicomponent aerosol models are not required for the retrieval of C.

  5. Observations of Aerosol Optical Properties over 15 AERONET Sites in Southeast Asia

    NASA Astrophysics Data System (ADS)

    Chan, J. D.; Lagrosas, N.; Uy, S. N.; Holben, B. N.; Dorado, S.; Tobias, V., Jr.; Anh, N. X.; Po-Hsiung, L.; Janjai, S.; Salinas Cortijo, S. V.; Liew, S. C.; Lim, H. S.; Lestari, P.

    2014-12-01

    Mean column-integrated optical properties from ground sun photometers of the Aerosol Robotic Network (AERONET) are studied to provide an overview of the characteristics of aerosols over the region as part of the 7 Southeast Asian Studies (7-SEAS) mission. The 15 AERONET sites with the most available level 2 data products are selected from Thailand (Chiang Mai, Mukdahan, Songkhla and Silpakorn University), Malaysia (University Sains Malaysia), Laos (Vientiane), Vietnam (Bac Giang, Bac Lieu and Nha Trang), Taiwan (National Cheng Kung University and Central Weather Bureau Taipei), Singapore, Indonesia (Bandung) and the Philippines (Manila Observatory and Notre Dame of Marbel University). For all 15 sites, high angstrom exponent values (α>1) have been observed. Chiang Mai and USM have the highest mean Angstrom exponent indicating the dominance of fine particles that can be ascribed to biomass burning and urbanization. Sites with the lowest Angstrom exponent values include Bac Lieu (α=1.047) and Manila Observatory (α=1.021). From the average lognormal size distribution curves, Songkhla and NDMU show the smallest annual variation in the fine mode region, indicating the observed fine aerosols are local to the sites. The rest of the sites show high variation which could be due to large scale forcings (e.g., monsoons and biomass burnings) that affect aerosol properties in these sites. Both high and low single scattering albedo at 440 nm (ω0440) values are found in sites located in major urban areas. Silpakorn University, Manila Observatory and Vientiane have all mean ω0440 < 0.90. Singapore and CWB Taipei have ω0440 > 0.94. The discrepancy in ω0 suggests different types of major emission sources present in urban areas. The absorptivity of urban aerosols can vary depending on the strength of traffic emissions, types of fuel combusted and automobile engines used, and the effect of biomass burning aerosols during the dry season. High aerosol optical depth values (τa550

  6. New Concepts In Retrieving Aerosol Properties Using MISR

    NASA Astrophysics Data System (ADS)

    Martonchik, J.; Diner, D.; Kahn, R.; Bull, M.; Paradise, S.; Gaitley, B.; Garay, M.

    2006-12-01

    Since March 2000 the nine camera Multi-angle Imaging SpectroRadiometer (MISR) aboard NASA's EOS Terra platform has been providing information about aerosols over both land and ocean. During this period many incremental improvements to the individual ocean and land aerosol retrieval algorithms have been made but the fundamental ideas behind each have remained essentially unchanged. Here we explore some new algorithmic concepts, multiangular in nature, which may provide a considerable increase in the accuracy of retrieved aerosol properties from space. The current MISR retrieval algorithm over ocean nominally utilizes only the red (672 nm) and near IR (866 nm) spectral bands, assuming that neither band has any significant contamination from water-leaving radiance (WLR). This approach provides a good determination of aerosol optical depth but the retrieved Angstrom exponent is subject to much more uncertainty because of the relatively small wavelength separation of the red and near IR bands. The concept being explored for improving the ocean algorithm is to also include the remaining blue (446 nm) and green (558 nm) MISR bands under the assumptions that 1) only the near IR band has near-zero WLR and 2) the WLR in the remaining three bands is isotropic. An algorithm with these conditions should provide a more accurate retrieval of aerosol properties and, simultaneously, the retrieval of WLR (ocean color). Over land the current aerosol retrieval algorithm is composed of two parts. The first is an angular shape comparison of the directional surface reflectance among the four MISR spectral bands, testing for similarity, a constraint that filters out the least probable aerosol models in the retrieval process. This procedure is then followed by a principal component analysis of the change in surface contrast with view angle and the final selection of retrieved aerosol models. This algorithm has produced high quality retrievals of aerosol optical depth over a wide variety of

  7. Ground-based Network and Supersite Measurements for Studying Aerosol Properties and Aerosol-Cloud Interactions

    NASA Technical Reports Server (NTRS)

    Tsay, Si-Chee; Holben, Brent N.

    2008-01-01

    From radiometric principles, it is expected that the retrieved properties of extensive aerosols and clouds from reflected/emitted measurements by satellite (and/or aircraft) should be consistent with those retrieved from transmitted/emitted radiance observed at the surface. Although space-borne remote sensing observations contain large spatial domain, they are often plagued by contamination of surface signatures. Thus, ground-based in-situ and remote-sensing measurements, where signals come directly from atmospheric constituents, the sun, and the Earth-atmosphere interactions, provide additional information content for comparisons that confirm quantitatively the usefulness of the integrated surface, aircraft, and satellite datasets. The development and deployment of AERONET (AErosol RObotic NETwork) sunphotometer network and SMART-COMMIT (Surface-sensing Measurements for Atmospheric Radiative Transfer - Chemical, Optical & Microphysical Measurements of In-situ Troposphere) mobile supersite are aimed for the optimal utilization of collocated ground-based observations as constraints to yield higher fidelity satellite retrievals and to determine any sampling bias due to target conditions. To characterize the regional natural and anthropogenic aerosols, AERONET is an internationally federated network of unique sunphotometry that contains more than 250 permanent sites worldwide. Since 1993, there are more than 480 million aerosol optical depth observations and about 15 sites have continuous records longer than 10 years for annual/seasonal trend analyses. To quantify the energetics of the surface-atmosphere system and the atmospheric processes, SMART-COMMIT instrument into three categories: flux radiometer, radiance sensor and in-situ probe. Through participation in many satellite remote-sensing/retrieval and validation projects over eight years, SMART-COMMIT have gradually refine( and been proven vital for field deployment. In this paper, we will demonstrate the

  8. The T1-T2 Study: Evolution of Aerosol Properties Downwind of Mexico City

    SciTech Connect

    Doran, J C; Barnard, James C; Arnott, W P; Cary, R; Coulter, Richard L; Fast, Jerome D; Kassianov, Evgueni I; Kleinman, Lawrence I; Laulainen, Nels S; Martin, Tim J; Paredes-Miranda, Guadalupe L; Pekour, Mikhail S; Shaw, William J; Smith, D F; Springston, Stephen R; Yu, Xiao-Ying

    2007-03-23

    As part of a major atmospheric chemistry and aerosol field program carried out in March of 2006, a study was conducted in the area to the north and northeast of Mexico City to investigate the evolution of aerosols and their associated optical properties in the first few hours after their emission. The focus of the T1-T2 aerosol study was to investigate changes in the specific absorption αABS (absorption per unit mass, with unit of m2g-1) of black carbon as it aged and became coated with compounds such as sulfate and organic carbon, evolving from an external to an internal mixture. Such evolution has been reported in previous studies. The T1 site was located just to the north of the Mexico City metropolitan area; the T2 site was situated approximately 35 km farther to the northeast. Nephelometers, particle soot absorption photometers, photoacoustic absorption photometers, and organic and elemental carbon analyzers were used to measure the optical properties of the aerosols and the carbon concentrations at each of the sites. Radar wind profilers and radiosonde systems helped to characterize the meteorology and to identify periods when transport from Mexico City over T1 and T2 occurred. Organic and elemental carbon concentrations at T1 showed diurnal cycles reflecting the nocturnal and early morning buildup from nearby sources, while concentrations at T2 appeared to be more affected by transport from Mexico City. Specific absorption during transport periods was lower than during other times, consistent with the likelihood of fresher emissions being found when the winds blew from Mexico City over T1 and T2. The specific absorption at T2 was larger than at T1, which is also consistent with the expectation of more aged particles with encapsulated black carbon being found at the more distant location. In situ measurements of single scattering albedo with an aircraft and a ground station showed general agreement with column-averaged values derived from rotating shadowband

  9. Airborne differential absorption lidar system for measurements of atmospheric water vapor and aerosols

    NASA Technical Reports Server (NTRS)

    Carter, Arlen F.; Allen, Robert J.; Mayo, M. Neale; Butler, Carolyn F.; Grossman, Benoist E.; Ismail, Syed; Grant, William B.; Browell, Edward V.; Higdon, Noah S.; Mayor, Shane D.; Ponsardin, Patrick; Hueser, Alene W.

    1994-01-01

    An airborne differential absorption lidar (DIAL) system has been developed at the NASA Langley Research Center for remote measurements of atmospheric water vapor (H2O) and aerosols. A solid-state alexandrite laser with a 1-pm linewidth and greater than 99.85% spectral purity was used as the on-line transmitter. Solid-state avalanche photodiode detector technology has replaced photomultiplier tubes in the receiver system, providing an average increase by a factor of 1.5-2.5 in the signal-to-noise ratio of the H2O measurement. By incorporating advanced diagnostic and data-acquisition instrumentation into other subsystems, we achieved additional improvements in system operational reliability and measurement accuracy. Laboratory spectroscopic measurements of H2O absorption-line parameters were performed to reduce the uncertainties in our knowledge of the absorption cross sections. Line-center H2O absorption cross sections were determined, with errors of 3-6%, for more than 120 lines in the 720-nm region. Flight tests of the system were conducted during 1989-1991 on the NASA Wallops Flight Facility Electra aircraft, and extensive intercomparison measurements were performed with dew-point hygrometers and H2O radiosondes. The H2O distributions measured with the DIAL system differed by less than 10% from the profiles determined with the in situ probes in a variety of atmospheric conditions.

  10. Airborne differential absorption lidar system for measurements of atmospheric water vapor and aerosols.

    PubMed

    Higdon, N S; Browell, E V; Ponsardin, P; Grossmann, B E; Butler, C F; Chyba, T H; Mayo, M N; Allen, R J; Heuser, A W; Grant, W B; Ismail, S; Mayor, S D; Carter, A F

    1994-09-20

    An airborne differential absorption lidar (DIAL) system has been developed at the NASA Langley Research Center for remote measurements of atmospheric water vapor (H(2)O) and aerosols. A solid-state alexandrite laser with a 1-pm linewidth and > 99.85% spectral purity was used as the on-line transmitter. Solid-state avalanche photodiode detector technology has replaced photomultiplier tubes in the receiver system, providing an average increase by a factor of 1.5-2.5 in the signal-to-noise ratio of the H(2)O measurement. By incorporating advanced diagnostic and data-acquisition instrumentation into other subsystems, we achieved additional improvements in system operational reliability and measurement accuracy. Laboratory spectroscopic measurements of H(2)O absorption-line parameters were perfo med to reduce the uncertainties in our knowledge of the absorption cross sections. Line-center H(2)O absorption cross sections were determined, with errors of 3-6%, for more than 120 lines in the 720-nm region. Flight tests of the system were conducted during 1989-1991 on the NASA Wallops Flight Facility Electra aircraft, and extensive intercomparison measurements were performed with dew-point hygrometers and H(2)O radiosondes. The H(2)O distributions measured with the DIAL system differed by ≤ 10% from the profiles determined with the in situ probes in a variety of atmospheric conditions.

  11. Airborne differential absorption lidar system for measurements of atmospheric water vapor and aerosols.

    PubMed

    Higdon, N S; Browell, E V; Ponsardin, P; Grossmann, B E; Butler, C F; Chyba, T H; Mayo, M N; Allen, R J; Heuser, A W; Grant, W B; Ismail, S; Mayor, S D; Carter, A F

    1994-09-20

    An airborne differential absorption lidar (DIAL) system has been developed at the NASA Langley Research Center for remote measurements of atmospheric water vapor (H(2)O) and aerosols. A solid-state alexandrite laser with a 1-pm linewidth and > 99.85% spectral purity was used as the on-line transmitter. Solid-state avalanche photodiode detector technology has replaced photomultiplier tubes in the receiver system, providing an average increase by a factor of 1.5-2.5 in the signal-to-noise ratio of the H(2)O measurement. By incorporating advanced diagnostic and data-acquisition instrumentation into other subsystems, we achieved additional improvements in system operational reliability and measurement accuracy. Laboratory spectroscopic measurements of H(2)O absorption-line parameters were perfo med to reduce the uncertainties in our knowledge of the absorption cross sections. Line-center H(2)O absorption cross sections were determined, with errors of 3-6%, for more than 120 lines in the 720-nm region. Flight tests of the system were conducted during 1989-1991 on the NASA Wallops Flight Facility Electra aircraft, and extensive intercomparison measurements were performed with dew-point hygrometers and H(2)O radiosondes. The H(2)O distributions measured with the DIAL system differed by ≤ 10% from the profiles determined with the in situ probes in a variety of atmospheric conditions. PMID:20941181

  12. Retrieval of Aerosol Optical Properties under Thin Cirrus from MODIS

    NASA Technical Reports Server (NTRS)

    Lee, Jaehwa; Hsu, Nai-Yung Christina; Bettenhausen, Corey; Sayer, Andrew Mark.

    2014-01-01

    Retrieval of aerosol optical properties using shortwave bands from passive satellite sensors, such as MODIS, is typically limited to cloud-free areas. However, if the clouds are thin enough (i.e. thin cirrus) such that the satellite-observed reflectance contains signals under the cirrus layer, and if the optical properties of this cirrus layer are known, the TOA reflectance can be corrected for the cirrus layer to be used for retrieving aerosol optical properties. To this end, we first correct the TOA reflectances in the aerosol bands (0.47, 0.55, 0.65, 0.86, 1.24, 1.63, and 2.12 micron for ocean algorithm and 0.412, 0.47, and 0.65 micron for deep blue algorithm) for the effects of thin cirrus using 1.38 micron reflectance and conversion factors that convert cirrus reflectance in 1.38 micron band to those in aerosol bands. It was found that the conversion factors can be calculated by using relationships between reflectances in 1.38 micron band and minimum reflectances in the aerosol bands (Gao et al., 2002). Refer to the example in the figure. Then, the cirrus-corrected reflectance can be calculated by subtracting the cirrus reflectance from the TOA reflectance in the optically thin case. A sensitivity study suggested that cloudy-sky TOA reflectances can be calculated with small errors in the form of simple linear addition of cirrus-only reflectances and clear-sky reflectances. In this study, we correct the cirrus signals up to TOA reflectance at 1.38 micron of 0.05 where the simple linear addition is valid without extensive radiative transfer simulations. When each scene passes the set of tests shown in the flowchart, the scene is corrected for cirrus contamination and passed into aerosol retrieval algorithms.

  13. Aerosol light absorption, black carbon, and elemental carbon at the Fresno Supersite, California

    NASA Astrophysics Data System (ADS)

    Chow, Judith C.; Watson, John G.; Doraiswamy, Prakash; Chen, Lung-Wen Antony; Sodeman, David A.; Lowenthal, Douglas H.; Park, Kihong; Arnott, W. Patrick; Motallebi, Nehzat

    2009-08-01

    Particle light absorption ( bap), black carbon (BC), and elemental carbon (EC) measurements at the Fresno Supersite during the summer of 2005 were compared to examine the equivalency of current techniques, evaluate filter-based bap correction methods, and determine the EC mass absorption efficiency (σ ap) and the spectral dependence of bap. The photoacoustic analyzer (PA) was used as a benchmark for in-situ bap. Most bap measurement techniques were well correlated ( r ≥ 0.95). Unadjusted Aethalometer (AE) and Particle Soot Absorption Photometer (PSAP) bap were up to seven times higher than PA bap at similar wavelengths because of absorption enhancement by backscattering and multiple scattering. Applying published algorithms to correct for these effects reduced the differences to 24 and 17% for the AE and PSAP, respectively, at 532 nm. The Multi-Angle Absorption Photometer (MAAP), which accounts for backscattering effects, overestimated bap relative to the PA by 51%. BC concentrations determined by the AE, MAAP, and Sunset Laboratory semi-continuous carbon analyzer were also highly correlated ( r ≥ 0.93) but differed by up to 57%. EC measured with the IMPROVE/STN thermal/optical protocols, and the French two-step thermal protocol agreed to within 29%. Absorption efficiencies determined from PA bap and EC measured with different analytical protocols averaged 7.9 ± 1.5, 5.4 ± 1.1, and 2.8 ± 0.6 m 2/g at 532, 670, and 1047 nm, respectively. The Angström exponent (α) determined from adjusted AE and PA bap ranged from 1.19 to 1.46. The largest values of α occurred during the afternoon hours when the organic fraction of total carbon was highest. Significant biases associated with filter-based measurements of bap, BC, and EC are method-specific. Correcting for these biases must take into account differences in aerosol concentration, composition, and sources.

  14. Estimate of the aerosol properties over the ocean with POLDER

    NASA Astrophysics Data System (ADS)

    Deuzé, J. L.; Goloub, P.; Herman, M.; Marchand, A.; Perry, G.; Susana, S.; Tanré, D.

    2000-06-01

    The wide field of view imaging spectroradiometer Polarization and Directionality of the Earth's Reflectance (POLDER) developed by Centre National d'Etudes Spatiales and operated aboard the Japanese heliosynchronous platform Advanced Earth Observation Satellite (ADEOS) from October 30, 1996, to June 30, 1997, provided the first global systematic measurements of the spectral, directional, and polarized characteristics of the solar radiation reflected by the Earth/atmosphere system. These original observational capabilities offer an opportunity to enhance the characterization of several components of the global environment, especially the oceanic and terrestrial vegetal primary production, the aerosol physical and optical properties, and the tridimensional structure and microphysics of clouds. Here we examine the remote sensing of aerosols over the oceans. In a first step the aerosol optical thickness and Ångström exponent are derived from the radiance measurements. In a second step the polarization measurements are used for the retrieval of the aerosol refractive index. The inversion algorithm assumes spherical, nonabsorbing particles with monomodal lognormal size distribution. The adequacy of this modeling is discussed for a representative set of aerosol observations. Successful retrieval is generally achieved in the presence of small aerosols with Ångström exponent larger than ˜1.0. For such particles, polarization may provide information on the particle refractive index. As the Ångstrom exponent of the particle decreases, the data fitting residual errors increase, especially in polarized light, which prevents the retrieval of the aerosol refractive index. The trends of the discrepancies point out two shortcomings of the aerosol modeling. The theoretical results systematically underestimate the contribution of small polarizing particles in the polarization measurements for side-scattering angles ranging from 80° to 120°. This indicates very probably that

  15. Investigation on seasonal variations of aerosol properties and its influence on radiative effect over an urban location in central India

    NASA Astrophysics Data System (ADS)

    Jose, Subin; Gharai, Biswadip; Niranjan, K.; Rao, P. V. N.

    2016-05-01

    Aerosol plays an important role in modulating solar radiation, which are of great concern in perspective of regional climate change. The study analysed the physical and optical properties of aerosols over an urban area and estimated radiative effect using three years in-situ data from sunphotometer, aethalometer and nephelometer as input to radiative transfer model. Aerosols properties indicate the dominance of fine mode aerosols over the study area. However presence of coarse mode aerosols is also found during pre-monsoon [March-April-May]. Daily mean aerosol optical depth showed a minimum during winter [Dec-Jan-Feb] (0.45-0.52) and a maximum during pre-monsoon (0.6-0.7), while single scattering albedo (ω) attains its maximum (0.78 ± 0.05) in winter and minimum (0.67 ± 0.06) during pre-monsoon and asymmetry factor varied in the range between 0.48 ± 0.02 to 0.53 ± 0.04. Episodic events of dust storm and biomass burning are identified by analyzing intrinsic aerosol optical properties like scattering Ångström exponent (SAE) and absorption Ångström exponent (AAE) during the study periods and it has been observed that during dust storm events ω is lower (˜0.77) than that of during biomass burning (˜0.81). The aerosol direct radiative effect at top of the atmosphere during winter is -11.72 ± 3.5 Wm-2, while during pre-monsoon; it is -5.5 ± 2.5 Wm-2, which can be due to observed lower values of ω during pre-monsoon. A large positive enhancement of atmospheric effect of ˜50.53 Wm-2 is observed during pre-monsoon compared to winter. Due to high aerosol loading in pre-monsoon, a twofold negative surface forcing is also observed in comparison to winter.

  16. Aerosol Properties From Combined Oxygen A Band Radiances and Lidar

    NASA Technical Reports Server (NTRS)

    Winker, Dave; Zhai, Peng-Wang; Hu, Yongxiang

    2015-01-01

    We have developed a new aerosol retrieval technique based on combing high-resolution A band spectra with lidar profiles. Our goal is the development of a technique to retrieve aerosol absorption, one of the critical parameters affecting the global radiation budget and one which is currently poorly constrained by satellite measurements. Our approach relies on two key factors: 1) the use of high spectral resolution (17,000:1) measurements which resolve the A-band line structure, and 2) the use of co-located lidar profile measurements to constrain the vertical distribution of scatterers in the forward model. The algorithm has been developed to be applied to observations from the CALIPSO and OCO-2 satellites, flying in formation as part of the A-train constellation. We describe the approach and present simulated retrievals to illustrate performance potential.

  17. Properties of quasar broad absorption line outflows

    NASA Astrophysics Data System (ADS)

    Capellupo, Daniel Moshin

    2012-06-01

    Broad absorption lines (BALs) in quasar spectra identify high velocity outflows that likely exist in all quasars and could play a major role in feedback to galaxy evolution. In this dissertation, I use two methods to illuminate important properties of these outflows with the goal of a better understanding of these outflow systems and ultimately of the connection between quasars and their host galaxies. The variability of BALs can help us understand the structure, evolution, and basic physical properties of the outflows. I report here on a BAL monitoring programme of a sample of 24 luminous quasars at redshifts 1.2absorption to try to ascertain the cause(s) of the variability. I find that Si IV BALs are more likely to vary than C IV BALs. When both C IV and Si IV varied, those changes always occurred in the same sense (either getting weaker or stronger). The multi-epoch data, including up to 10 epochs of data per quasar, show that the BAL changes were not generally monotonic across the full ˜5 to ˜8 yr time span of our observations, suggesting that the characteristic time-scale for significant line variations, and (perhaps) for structural changes in the outflows, is less than a few years. The evidence presented here indicates that the cause of variability is likely a complex mixture of changing ionization in the outflowing

  18. A Study of Morphology and Magnetic Properties of Doped Barium Ferrite Films Formed by Aerosol Deposition

    NASA Astrophysics Data System (ADS)

    Johnson, Scooter; Gonzalez, Christopher; Robinson, Zachary; Ellsworth, David; Wu, Mingzhong

    Aerosol deposition is a room-temperature thick film deposition technique that produces polycrystalline films that have > 95% of theoretical density and are up to several hundred microns thick. In addition to depositing films at room temperature another distinct advantage of aerosol deposition is the ability to produce films with the same resulting stoichiometry as the starting material. For this work, we deposited a proprietary doped barium ferrite (BaFe12O19) film from powder produced by Temex Ceramics. This material is designed for microwave absorption near 18 GHz via ferromagnetic resonance. We compare the structural and magnetic properties of the as-deposited film, bulk material, and starting powder. For this purpose, we employed scanning electron microscopy, x-ray photoemission spectroscopy, x-ray diffraction, vibrating sample magnetometry, and broad-band ferromagnetic resonance characterization techniques.

  19. Aerosol Light Absorption and Scattering in Mexico City: Comparison With Las Vegas, NV, and Los Angeles, CA.

    NASA Astrophysics Data System (ADS)

    Paredes-Miranda, G.; Arnott, W. P.; Gaffney, J. S.; Marley, N. A.; Campbell, D.; Fujita, E.

    2007-12-01

    Aerosol light scattering and absorption measurements were deployed in and near Mexico City in March 2006 as part of the Megacity Impacts on Regional and Global Environments (MIRAGE). The primary site in Mexico City was an urban site at Instituto Mexicano del Petroleo (Mexican Oil Institute, denoted by IMP). Similar campaigns were held in Las Vegas, NV in January-February, 2003; and Los Angeles, CA at numerous sites during all seasons from 2003 through 2007. The IMP site gave in-situ characterization of the Mexico City plume under favorable wind conditions. The photoacoustic instrument (PAS) used at IMP operates at 532 nm, and conveniently allowed for characterization of gaseous absorption at this wavelength as well. Light scattering measurements are accomplished within the PAS by the reciprocal nephelometery method. In Mexico City the aerosol absorption coefficient typically varies between 20 and 180 Mm-1 during the course of the day and significant diurnal variation of the aerosol single scattering albedo was observed probably as a consequence of secondary aerosol formation. We will present the diurnal variation of the scattering and absorption as well as the single scattering albedo and fraction of absorption due to gases at the IMP site and compare with Las Vegas diurnal variation. Mexico City 'breaths' more during the course of the day than Las Vegas, Nevada in part because the latitude of Mexico City resulted in more direct solar radiation. Further insight on the meteorological connections and population dynamics will be discussed.

  20. Absorption coefficient of urban aerosol in Nanjing, west Yangtze River Delta, China

    NASA Astrophysics Data System (ADS)

    Zhuang, B. L.; Wang, T. J.; Liu, J.; Ma, Y.; Yin, C. Q.; Li, S.; Xie, M.; Han, Y.; Zhu, J. L.; Yang, X. Q.; Fu, C. B.

    2015-12-01

    Absorbing aerosols can significantly modulate short-wave solar radiation in the atmosphere, affecting regional and global climate. The aerosol absorption coefficient (AAC) is an indicator that assesses the impact of absorbing aerosols on radiative forcing. In this study, the near-surface AAC and absorption Ångström exponent (AAE) in the urban area of Nanjing, China, are characterized on the basis of measurements in 2012 and 2013 using the seven-channel Aethalometer (model AE-31, Magee Scientific, USA). The AAC is estimated with direct and indirect corrections, which result in consistent temporal variations and magnitudes of AAC at 532 nm. The mean AAC at 532 nm is about 43.23 ± 28.13 M m-1 in the urban area of Nanjing, which is much lower than that in Pearl River Delta and the same as in rural areas (Lin'an) in Yangtze River Delta. The AAC in the urban area of Nanjing shows strong seasonality (diurnal variations); it is high in cold seasons (at rush hour) and low in summer (in the afternoon). It also shows synoptic and quasi-2-week cycles in response to weather systems. Its frequency distribution follows a typical log-normal pattern. The 532 nm AAC ranging from 15 to 65 M m-1 dominates, accounting for more than 72 % of the total data samples in the entire study period. Frequent high pollution episodes, such as those observed in June 2012 and in winter 2013, greatly enhanced AAC and altered its temporal variations and frequency distributions. These episodes are mostly due to local emissions and regional pollution. Air masses flowing from northern China to Nanjing can sometimes be highly polluted and lead to high AAC at the site. AAE at 660/470 nm from the Schmid correction (Schmid et al., 2006) is about 1.56, which might be more reasonable than from the Weingartner correction (Weingartner et al., 2003). Low AAEs mainly occur in summer, likely due to high relative humidity (RH) in the season. AAC increases with increasing AAE at a fixed aerosol loading. The RH

  1. Application of aerosol optical properties to estimate aerosol type from ground-based remote sensing observation at urban area of northeastern China

    NASA Astrophysics Data System (ADS)

    Che, Huizheng; Zhao, Hujia; Wu, Yunfei; Xia, Xiangao; Zhu, Jun; Dubovik, Oleg; Estelles, Victor; Ma, Yanjun; Wang, Yangfeng; Wang, Hong; Wang, Yaqiang; Zhang, Xiaoye; Shi, Guangyu

    2015-09-01

    Aerosol optical properties were derived from ground-based sunphotometer observations between 2009-2013 at three urban sites of Shenyang, Anshan, Fushun in northeastern China. The annual means for extinction aerosol optical depths (EAOD) at 500 nm were 0.57±0.38, 0.52±0.35, and 0.41±0.31 at Shenyang, Anshan, Fushun, respectively. The corresponding annual means for the extinction Angstrom exponents (EAE) computed for the wavelengths of 440 and 870 nm were 0.86±0.32, 0.86±0.34 and 0.91±0.35, respectively, indicating that urban area of Northeast China were affected by both coarse and fine particles. Hygroscopic growth in summer and incursions of dust aerosols in spring were evidently revealed from the analysis of the relationship between EAE and δEAE (the EAE difference, δEAE=EAE(440,670)-EAE(670,870)). The annual mean absorption aerosol optical depths (AAOD440 nm) values at Shenyang, Anshan, Fushun were 0.15±0.11, 0.10±0.07, 0.08±0.04, respectively. The annual mean absorption Angstrom exponents (AAE440-870 nm) values were 0.86±0.24, 1.19±0.39, 1.33±0.36 at Shenyang, Anshan, Fushun, respectively. When the AAEs were close to unity at Anshan, the absorption aerosol particles evidently consisted of black carbon from coal combustion and motor vehicles. Larger AAEs at Fushun were indicative of absorbing aerosols mainly from biomass burning and mineral dust. The AAE at Shenyang was<1 which may be consistent with black carbon particles with absorbing or non-absorbing coatings. Analysis of the relationship between the AAEs and extinction Angstrom exponents showed that the aerosol populations at these three sites could be classified as "mixed-small particles" including anthropogenic particles and secondary organic aerosol with highly variable sphericity fractions.

  2. Relations Between Cloud Condensation Nuclei And Aerosol Optical Properties Relevant to Remote Sensing: Airborne Measurements in Biomass Burning, Pollution and Dust Aerosol Over North America

    NASA Astrophysics Data System (ADS)

    Shinozuka, Y.; Clarke, A.; Howell, S.; Kapustin, V.; McNaughton, C.; Zhou, J.; Decarlo, P.; Jimenez, J.; Roberts, G.; Tomlinson, J.; Collins, D.

    2008-12-01

    Remote sensing of the concentration of cloud condensation nuclei (CCN) would help investigate the indirect effect of tropospheric aerosols on clouds and climate. In order to assess its feasibility, this paper evaluates the spectral-based retrieval technique for aerosol number and seeks one for aerosol solubility, using in-situ aircraft measurements of aerosol size distribution, chemical composition, hygroscopicity, CCN activity and optical properties. Our statistical analysis reveals that the CCN concentration over Mexico can be optically determined to a relative error of <20%, smaller than that for the mainland US and the surrounding oceans (~a factor of 2). Mexico's advantage is four-fold. Firstly, many particles originating from the lightly regulated industrial combustion and biomass burning are large enough to significantly affect light extinction, elevating the correlation between extinction and CCN number in absence of substantial dust. Secondly, the generally low ambient humidity near the major aerosol sources limits the error in the estimated response of particle extinction to humidity changes. Thirdly, because many CCN contain black carbon, light absorption also provides a measure of the CCN concentration. Fourthly, the organic fraction of volatile mass of submicron particles (OMF) is anti-correlated with the wavelength dependence of extinction due to preferential anion uptake by coarse dust, which provides a potential tool for remote-sensing OMF and the particle solubility.

  3. Seasonal variability of optical properties of aerosols in the Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Vrekoussis, M.; Liakakou, E.; Koçak, M.; Kubilay, N.; Oikonomou, K.; Sciare, J.; Mihalopoulos, N.

    The aerosol optical properties (scattering and absorption coefficients) were investigated at two remote locations in the Eastern Mediterranean in conjunction with aerosol ion composition measurements: Finokalia in the Crete Island in Greece (March 2001-June 2002) and Erdemli in Turkey (July 1999-June 2000). Ambient light-scattering coefficient ( σsp-532 nm ) at Finokalia had a mean value of 50±23 Mm -1 while at Erdemli this value was 90±160 Mm -1, due to a severe dust event that occurred from 17 to 19 April 2000. Scattering coefficients up to 5000 Mm -1 were encountered during the transition periods (spring and autumn) and were associated with dust storm events. During these events significant correlations were observed between dust and σsp and mass scattering efficiencies of 0.21 and 0.96 m 2g -1 were calculated for dust for Finokalia and Erdemli, respectively. Significant correlations were also observed at both locations between non-sea-salt sulphate (nss-SO 42-); σsp and mass scattering efficiencies of 5.9±1.8 and 5.7±1.4 m 2g -1 were calculated for the nss-SO 42- at Finokalia and Erdemli, respectively. At Finokalia absorption measurements were also performed at the same time and the mean absorption coefficient ( σap-565 nm ) was found to be 5.6±3.6 Mm -1. Maxima of absorption coefficient were associated with two distinct meteorological situations indicative of pollution transported from northern Europe and Saharan dust events. Saharan dust can therefore significantly contribute to both scattering and absorption of solar radiation, the latter due to its hematite content. Based on scattering and absorption measurements, an annual mean single-scattering albedo ( ω) adjusted at 550 nm of 0.89±0.04 was calculated for Finokalia. Finally, radiative forcing efficiency (RFE) over the sea at 550 nm induced by aerosols has been calculated for Finokalia. RFE follows a clear seasonal variation, with the lowest mean values during summer (-73W m -2) and the highest

  4. Inferring brown carbon content from UV aerosol absorption measurements during biomass burning season

    NASA Astrophysics Data System (ADS)

    Mok, J.; Krotkov, N. A.; Arola, A. T.; Torres, O.; Jethva, H. T.; Andrade, M.; Labow, G. J.; Eck, T. F.; Li, Z.; Dickerson, R. R.; Stenchikov, G. L.; Osipov, S.

    2015-12-01

    Measuring spectral dependence of light absorption by colored organic or "brown" carbon (BrC) is important, because of its effects on photolysis rates of ozone and surface ultraviolet (UV) radiation. Enhanced UV spectral absorption by BrC can in turn be exploited for simultaneous retrievals of BrC and black carbon (BC) column amounts in field campaigns. We present an innovative ground-based retrieval of BC and BrC volume fractions and their mass absorption efficiencies during the biomass burning season in Santa Cruz, Bolivia in September-October 2007. Our method combines retrieval of BC volume fraction using AERONET inversion in visible wavelengths with the inversion of total BC+BrC absorption (i.e., column effective imaginary refractive index, kmeas) using Diffuse/Direct irradiance measurements in UV wavelengths. First, we retrieve BrC volume fraction by fitting kmeas at 368nm using Maxwell-Garnett (MG) mixing rules assuming: (1) flat spectral dependence of kBC, (2) known value of kBrC at 368nm from laboratory absorption measurements or smoke chamber experiments, and (3) known BC volume fraction from AERONET inversion. Next, we derive kBrC in short UVB wavelengths by fitting kmeas at 305nm, 311nm, 317nm, 325nm, and 332nm using MG mixing rules and fixed volume fractions of BC and BrC. Our retrievals show larger than expected spectral dependence of kBrC in UVB wavelengths, implying reduced surface UVB irradiance and inhibited photolysis rates of surface ozone destruction. We use a one-dimensional chemical box model to show that the observed strong wavelength dependence of BrC absorption leads to inhibited photolysis of ozone to O(1D), a loss mechanism, while having little impact or even accelerating photolysis of NO2, an ozone production mechanism. Although BC only absorption in biomass burning aerosols is important for climate radiative forcing in the visible wavelengths, additional absorption by BrC is important because of its impact on surface UVB radiation

  5. A perspective on SOA generated in aerosol water from glyoxal and methylglyoxal and its impacts on climate-relevant aerosol properties

    NASA Astrophysics Data System (ADS)

    Sareen, N.; McNeill, V. F.

    2011-12-01

    . These compounds included (hemi)acetals, aldol condensation products, and oligomeric species up to 759 amu. Since these products are vulnerable to oxidants such as O3 and OH in the atmosphere, kinetic studies were conducted to study their affect upon exposure to O3 and OH. Custom-designed flow tube reactors were coupled with the Aerosol-CIMS to monitor aerosol composition, and consequently this data was used to determine reactive uptake coefficients (γO3~10-8 and γOH~ 10-6). Additionally, the lifetime of these SOA species in the atmosphere can be estimated and if these time scales are sufficiently long, they may affect aerosol optical properties. The effect of oxidation on the optical properties is also currently being tested by collecting aerosol particles before and after oxidation on a quartz window and testing changes in absorption using the UV-Vis spectrophotometer. The results of all these studies will be integrated to understand the role of methylglyoxal as a SOA precursor and the effect on various aerosol properties, and this will be used as a model system to predict the fate of similar organics in the atmosphere.

  6. Simultaneous retrieval of aerosol properties and clear-sky direct radiative effect over the global ocean from MODIS

    NASA Astrophysics Data System (ADS)

    Lee, Jaehwa; Kim, Jhoon; Lee, Yun Gon

    2014-08-01

    A unified satellite algorithm is presented to simultaneously retrieve aerosol properties (aerosol optical depth; AOD and aerosol type) and clear-sky shortwave direct radiative effect (hereafter, DREA) over ocean. The algorithm is applied to Moderate Resolution Imaging spectroradiometer (MODIS) observations for a period from 2003 to 2010 to assess the DREA over the global ocean. The simultaneous retrieval utilizes lookup table (LUT) containing both spectral reflectances and solar irradiances calculated using a single radiative transfer model with the same aerosol input data. This study finds that aerosols cool the top-of-atmosphere (TOA) and bottom-of-atmosphere (BOA) by 5.2 ± 0.5 W/m2 and 8.3 W/m2, respectively, and correspondingly warm the atmosphere (hereafter, ATM) by 3.1 W/m2. These quantities, solely based on the MODIS observations, are consistent with those of previous studies incorporating chemical transport model simulations and satellite observations. However, the DREAs at BOA and ATM are expected to be less accurate compared to that of TOA due to low sensitivity in retrieving aerosol type information, which is related with the atmospheric heating by aerosols, particularly in low AOD conditions; consequently, the uncertainties could not be quantified. Despite the issue in the aerosol type information, the present method allows us to confine the DREA attributed only to fine-mode dominant aerosols, which are expected to be mostly anthropogenic origin, in the range from -1.1 W/m2 to -1.3 W/m2 at TOA. Improvements in size-resolved AOD and SSA retrievals from current and upcoming satellite instruments are suggested to better assess the DREA, particularly at BOA and ATM, where aerosol absorptivity induces substantial uncertainty.

  7. Measurements of Black Carbon and aerosol absorption during global circumnavigation and Arctic campaigns

    NASA Astrophysics Data System (ADS)

    Močnik, Griša; Drinovec, Luka; Vidmar, Primož; Lenarčič, Matevž

    2015-04-01

    During two flight campaigns: around the world (2012) and over the Arctic (2013) we demonstrated the feasibility of scientific research and aerial measurements of aerosolized Black Carbon with ultra-light aircraft. Conducted measurements provided first ever information on Black Carbon concentrations and sources over such a large area at altitude. Ground-level measurements of atmospheric aerosols are routinely performed around the world, but there exists very little data on their vertical and geographical distribution in the global atmosphere. These data is a crucial requirement for our understanding of the dispersion of pollutant species of anthropogenic origin, and their possible effects on radiative forcing, cloud condensation, and other phenomena which can contribute to adverse outcomes. Light absorbing carbonaceous aerosols and black carbon (BC) in particular are a unique tracer for combustion emissions, and can be detected rapidly and with great sensitivity by filter-based optical methods. A single-seat ultra-light aircraft flew around the world and on a Arctic expedition. The flights covered all seven continents; crossed all major oceans; and operated at altitudes around 3000 m ASL and up to 8900 m ASL. The aircraft carried a specially-developed high-sensitivity miniaturized dual-wavelength Aethalometer, which recorded BC concentrations with very high temporal resolution and sensitivity [1, 2]. We present examples of data from flight tracks over remote oceans, uninhabited land masses, and densely populated areas. Measuring the dependence of the aerosol absorption on the wavelength, we show that aerosols produced during biomass combustion can be transported to high altitude in high concentrations and we estimate the underestimation of the direct forcing by models assuming a simple linear relationship between BC concentration and forcing in comparison to observations [3,4]. 1. , Carbon Sampling Takes Flight, Science 2012, 335, 1286. 2. G. Močnik, L. Drinovec, M

  8. Characterization of the physical, chemical, and optical properties of atmospheric aerosol particles in New Hampshire

    NASA Astrophysics Data System (ADS)

    Slater, John Frederick

    Tropospheric aerosol particles directly affect the radiative budget of the Earth, and degrade visibility, by scattering and absorbing short-wavelength solar radiation. However, the radiative effect of aerosols is highly uncertain due to the non-uniform spatial distribution of the particles over Earth, their heterogeneous chemical composition, and their variable size. This dissertation quantifies some of the physical, chemical, and optical (radiative) properties of aerosols at different locations within New Hampshire (NH) from spring 2000 to fall 2001. During spring 2000, a 1-month study conducted at a mountaintop location adjacent to the White Mountain National Forest in northern NH showed that synoptic-scale air mass transport heavily influenced aerosol properties, and hence regional visibility. During W/SW flow, aerosol parameters and haziness were generally twice as high as times of N/NE flow. Similar transport dependent results were observed in October 2000 during a regional pollution event. Pollutants built-up in concentration during 22--28 October, culminated on 28 October, and then dropped 10-fold to background levels within a 6-hour period. Synoptic weather conditions during the transition from high to low pollutant levels indicated that an intense frontal boundary traversed the region, serving as a divide between a warm, humid, and polluted air mass from the W/SW, and a cold, dry, and clean air mass advancing out of Canada. Further work connecting air mass transport and aerosol variability in southern NH revealed that maximum aerosol optical depth (AOD) occurred in summer and was primarily associated with W/SW flow. Minimum AOD occurred in winter and was generally associated with N/NE flow. Mass scattering and absorption efficiencies of PM2.5 did not vary significantly between times of transport from different source regions and were very close to theoretical values. Maximum positive values of aerosol direct radiative forcing occurred in winter and maximum

  9. Aerosol Optical Properties and Chemical Composition Measured on the Ronald H. Brown During ACE-Asia

    NASA Astrophysics Data System (ADS)

    Quinn, P. K.; Bates, T. S.; Miller, T. L.; Coffman, D.

    2001-12-01

    Measurements of aerosol chemical, physical, and optical properties were made onboard the NOAA R/V Ronald H. Brown during the ACE-Asia Intensive Field Program to characterize Asian aerosol as it was transported across the Pacific Ocean. The ship traveled across the Pacific from Hawaii to Japan and into the East China Sea and the Sea of Japan. Trajectories indicate that remote marine air masses were sampled on the transit to Japan. In the ACE-Asia study region air masses from Japan, China, Mongolia, and the Korea Peninsula were sampled. A variety of aerosol types were encountered including those of marine, volcanic, crustal, and industrial origin. Presented here, for the different air masses encountered, are aerosol optical properties (scattering and absorption coefficients, single scattering albedo, Angstrom Exponent, and aerosol optical depth) and chemical composition (major ions, total organic and black carbon, and trace elements). Scattering by submicron aerosol (55 % RH and 550 nm) was less than 20 1/Mm during the transit from Hawaii to Japan. In continental air masses, values ranged from 60 to 320 1/Mm with the highest submicron scattering coefficients occurring during prefrontal conditions with a low marine boundary layer height and trajectories from Japan. For the continental air masses, the ratio of scattering by submicron to sub-10 micron aerosol during polluted conditions averaged 0.8 and during a dust event 0.41. Aerosol optical depth (500 nm) ranged from 0.08 during the Pacific transit to 1.3 in the prefrontal conditions described above. Optical depths during dust events ranged from 0.2 to 0.6. Submicron non-sea salt (nss) sulfate concentrations ranged from 0.5 ug/m-3 during the Pacific transit to near 30 ug/m-3 during the prefrontal conditions described above. Black carbon to total carbon mass ratios in air masses from Asia averaged 0.18 with highest values (0.32) corresponding to trajectories crossing the Yangtze River valley.

  10. Optical properties and aging of light-absorbing secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Liu, Jiumeng; Lin, Peng; Laskin, Alexander; Laskin, Julia; Kathmann, Shawn M.; Wise, Matthew; Caylor, Ryan; Imholt, Felisha; Selimovic, Vanessa; Shilling, John E.

    2016-10-01

    The light-absorbing organic aerosol (OA) commonly referred to as "brown carbon" (BrC) has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various volatile organic carbon (VOC) precursors, NOx concentrations, photolysis time, and relative humidity (RH) on the light absorption of selected secondary organic aerosols (SOA). Light absorption of chamber-generated SOA samples, especially aromatic SOA, was found to increase with NOx concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficient (MAC) value is observed from toluene SOA products formed under high-NOx conditions at moderate RH, in which nitro-aromatics were previously identified as the major light-absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organic nitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible (Vis) and ultraviolet (UV) light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.

  11. Primary and secondary contributions to aerosol light scattering and absorption in Mexico City during the MILAGRO 2006 campaign

    NASA Astrophysics Data System (ADS)

    Paredes-Miranda, G.; Arnott, W. P.; Jimenez, J. L.; Aiken, A. C.; Gaffney, J. S.; Marley, N. A.

    2008-09-01

    A photoacoustic spectrometer, a nephelometer, an aetholemeter, and an aerosol mass spectrometer were used to measure at ground level real-time aerosol light absorption, scattering, and chemistry at an urban site located in north east Mexico City (Instituto Mexicano del Petroleo, Mexican Petroleum Institute, denoted by IMP), as part of the Megacity Impact on Regional and Global Environments field experiment, MILAGRO, in March 2006. Photoacoustic and reciprocal nephelometer measurements at 532 nm accomplished with a single instrument compare favorably with conventional measurements made with an aethelometer and a TSI nephelometer. The diurnally averaged single scattering albedo at 532 nm was found to vary from 0.60 to 0.85 with the peak value at midday and the minimum value at 7 a.m. local time, indicating that the Mexico City plume is likely to have a net warming effect on local climate. The peak value is associated with strong photochemical generation of secondary aerosol. It is estimated that the same-day photochemical production of secondary aerosol (inorganic and organic) is approximately 40 percent of the aerosol mass concentration and light scattering in association with the peak single scattering albedo. A strong correlation of aerosol scattering at 532 nm and total aerosol mass concentration was found, and an average mass scattering efficiency factor of 3.8 m2/g was determined. Comparisons of photoacoustic and aethalometer light absorption with oxygenated organic aerosol concentration (OOA) indicate a very small systematic bias of the filter based measurement associated with OOA and the peak aerosol single scattering albedo.

  12. Primary and secondary contributions to aerosol light scattering and absorption in Mexico City during the MILAGRO 2006 campaign

    NASA Astrophysics Data System (ADS)

    Paredes-Miranda, G.; Arnott, W. P.; Jimenez, J. L.; Aiken, A. C.; Gaffney, J. S.; Marley, N. A.

    2009-06-01

    A photoacoustic spectrometer, a nephelometer, an aethalometer, and an aerosol mass spectrometer were used to measure at ground level real-time aerosol light absorption, scattering, and chemistry at an urban site located in North East Mexico City (Instituto Mexicano del Petroleo, Mexican Petroleum Institute, denoted by IMP), as part of the Megacity Impact on Regional and Global Environments field experiment, MILAGRO, in March 2006. Photoacoustic and reciprocal nephelometer measurements at 532 nm accomplished with a single instrument compare favorably with conventional measurements made with an aethalometer and a TSI nephelometer. The diurnally averaged single scattering albedo at 532 nm was found to vary from 0.60 to 0.85 with the peak value at midday and the minimum value at 07:00 a.m. local time, indicating that the Mexico City plume is likely to have a net warming effect on local climate. The peak value is associated with strong photochemical generation of secondary aerosol. It is estimated that the photochemical production of secondary aerosol (inorganic and organic) is approximately 75% of the aerosol mass concentration and light scattering in association with the peak single scattering albedo. A strong correlation of aerosol scattering at 532 nm and total aerosol mass concentration was found, and an average mass scattering efficiency factor of 3.8 m2/g was determined. Comparisons of photoacoustic and aethalometer light absorption with oxygenated organic aerosol concentration (OOA) indicate a very small systematic bias of the filter based measurement associated with OOA and the peak aerosol single scattering albedo.

  13. Influence of Delhi Pollution on Aerosol Properties Over Greater Noida

    NASA Astrophysics Data System (ADS)

    Sharma, M.; Singh, R. P.; Kumar, R.

    2015-12-01

    Influence of Delhi Pollution on Aerosol Properties over Greater NoidaManish Sharma1, Ramesh P. Singh2 and Rajesh Kumar3 1Research and Technology Development Centre, Sharda University, Greater Noida, India. 2School of Earth and Environmental Sciences, Schmid College of Science, Chapman University, Orange 92866, USA 3School of Basic Sciences and Research, Sharda University, Greater Noida, India. Delhi capital of India is highly polluted during winter and summer seasons. Due to dominant westerly winds the air mass influence its neighboring city Greater Noida which is located 60 km south east of Delhi. Detailed analysis of multi satellite data and ground observations have been carried out during 2001-2015. The ground observation and satellite data show dynamic aerosol optical parameters over Greater Noida. During winter and summer seasons, dominant westerly wind outflow pollutants of Delhi that mix with the local anthropogenic emissions of Greater Noida influencing aerosol properties at different pressure levels. The characteristics of trace gases and aerosol parameters over Delhi and Greater Noida will be presented. The air quality is severely affected from the outflow of pollutants from Delhi which is threat to people living in the area. Due to dominant winds the air mass further transported towards eastern parts of Indo-Gangetic plains affecting weather conditions of the major cities.

  14. Effective absorption cross sections and photolysis rates of anthropogenic and biogenic secondary organic aerosols

    NASA Astrophysics Data System (ADS)

    Romonosky, Dian E.; Ali, Nujhat N.; Saiduddin, Mariyah N.; Wu, Michael; Lee, Hyun Ji (Julie); Aiona, Paige K.; Nizkorodov, Sergey A.

    2016-04-01

    Mass absorption coefficient (MAC) values were measured for secondary organic aerosol (SOA) samples produced by flow tube ozonolysis and smog chamber photooxidation of a wide range of volatile organic compounds (VOC), specifically: α-pinene, β-pinene, β-myrcene, d-limonene, farnesene, guaiacol, imidazole, isoprene, linalool, ocimene, p-xylene, 1-methylpyrrole, and 2-methylpyrrole. Both low-NOx and high-NOx conditions were employed during the chamber photooxidation experiments. MAC values were converted into effective molecular absorption cross sections assuming an average molecular weight of 300 g/mol for SOA compounds. The upper limits for the effective photolysis rates of SOA compounds were calculated by assuming unity photolysis quantum yields and convoluting the absorption cross sections with a time-dependent solar spectral flux. A more realistic estimate for the photolysis rates relying on the quantum yield of acetone was also obtained. The results show that condensed-phase photolysis of SOA compounds can potentially occur with effective lifetimes ranging from minutes to days, suggesting that photolysis is an efficient and largely overlooked mechanism of SOA aging.

  15. Modeling of aerosol properties related to direct climate forcing

    NASA Astrophysics Data System (ADS)

    Koloutsou-Vakakis, Sotiria; Rood, Mark J.; Nenes, Athanasios; Pilinis, Christodoulos

    1998-07-01

    A long-term local experiment was designed with the purpose to accurately quantify aerosol parameters needed in order to estimate aerosol climate forcing at an anthropogenically perturbed continental site. Total light-scattering σλ,sp and backscattering σλ,bsp coefficients at wavelength λ, the hygroscopic growth factors with respect to scattering, ƒ(RH)λ,s, and the backscatter ratio bλ are the parameters considered in the paper. Reference and controlled relative humidity nephelometry measurements were taken at a ground level field sampling station, located near Bondville Illinois (40°03'12″N, W 88°22'19″W). Aerosol particle chemical composition and mass particle size distributions were also measured. The target parameters were also estimated from models. The modeling approach involved a two-step process. In the first step, aerosol properties were parameterized with an approach that made use of a modified thermodynamic equilibrium model, published laboratory measurements of single hygroscopic particle properties, and empirical mixing rules. In the second step, the parameterized aerosol properties were used as inputs into a code that calculate σλ,sp and σλ,bsp as functions of λ, RH, particle size, and composition. Comparison between the measured and the modeled results showed that depending on the assumptions, the differences between the modeled and observed results were within 5 to 28% for ƒ(RH)λ,s and within 22-35% for bλ at low RH and 0-20% for bλ at high RH. The temporal variation of the particle size distribution, the equilibrium state of the particles, and the hygroscopicity of the material characterized as residual were the major factors limiting the predictive ability of the models.

  16. Optical properties of aerosols over the eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Bryant, C.; Eleftheriadis, K.; Smolik, J.; Zdimal, V.; Mihalopoulos, N.; Colbeck, I.

    Measurements of aerosol optical properties, size distribution and chemical composition were conducted at Finokalia, a remote coastal site on the Greek island of Crete (35°19'N, 25°40'E) during July 2000 and January 2001. During the summer campaign the total scattering coefficient, σ, (at a wavelength of 550 nm) ranged from 13 to 120 Mm -1 (mean=44.2 Mm -1, standard deviation=17.5) whilst during the winter it ranged from 7.22 to 37.8 Mm -1 (mean=18.42 Mm -1, standard deviation=6.61). A distinct diurnal variation in scattering coefficients was observed, with minima occurring during the early morning and maxima in the late afternoon during the summer and late evening during the winter. The mean value of the Ångström exponent was 1.47 during the summer and 1.28 during the winter, suggesting a larger fraction of smaller particles at the site during the summer. This was confirmed by continuous measurements of the aerosol size distribution. An analysis of the single scattering albedo suggests that there is a more absorbing fraction in the particle composition in the summer than during the winter. An investigation of air mass origins on aerosol optical properties indicated that those from Turkey and Central/Eastern Europe were highly polluted with a corresponding impact on aerosol optical properties. A linear relationship was obtained between the total scattering coefficient and both the non-sea-salt sulphate concentrations and the fine aerosol fraction.

  17. Aerosols physical properties at Hada Al Sham, western Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Lihavainen, H.; Alghamdi, M. A.; Hyvärinen, A.-P.; Hussein, T.; Aaltonen, V.; Abdelmaksoud, A. S.; Al-Jeelani, H.; Almazroui, M.; Almehmadi, F. M.; Al Zawad, F. M.; Hakala, J.; Khoder, M.; Neitola, K.; Petäjä, T.; Shabbaj, I. I.; Hämeri, K.

    2016-06-01

    This is the first time to clearly derive the comprehensive physical properties of aerosols at a rural background area in Saudi Arabia. Aerosol measurements station was established at a rural background area in the Western Saudi Arabia to study the aerosol properties. This study gives overview of the aerosol physical properties (PM10, PM2.5, black carbon and total number concentration) over the measurement period from November 2012 to February 2015. The average PM10 and PM2.5 concentrations were 95 ± 78 μg m-3 (mean ± STD, at ambient conditions) and 33 ± 68 μg m-3 (at ambient conditions), respectively. As expected PM10 concentration was dominated by coarse mode particles (PM10-PM2.5), most probably desert dust. Especially from February to June the coarse mode concentrations were high because of dust storm season. Aerosol mass concentrations had clear diurnal cycle. Lower values were observed around noon. This behavior is caused by wind direction and speed, during night time very calm easterly winds are dominating whereas during daytime the stronger westerly winds are dominating (sea breeze). During the day time the boundary layer is evolving, causing enhanced mixing and dilution leading to lower concentration. PM10 and PM2.5 concentrations were comparable to values measured at close by city of Jeddah. Black carbon concentration was about 2% and 6% of PM10 and PM2.5 mass, respectively. Total number concentration was dominated by frequent new particle formation and particle growth events. The typical diurnal cycle in particle total number concentration was clearly different from PM10 and PM2.5.

  18. Hygroscopic properties of levoglucosan and related organic compounds characteristic to biomass burning aerosol particles

    NASA Astrophysics Data System (ADS)

    Mochida, Michihiro; Kawamura, Kimitaka

    2004-11-01

    Biomass burning, which is characterized by pyrolysis as well as vaporization and condensation of biomass constituents, is a significant source of atmospheric organic aerosols. In this study, hygroscopic properties of five organic compounds (levoglucosan, D-glucose, and vanillic, syringic, and 4-hydroxybenozoic acids), which are major pyrolysis products of wood, were measured using a tandem differential mobility analyzer. Levoglucosan, which is typically the most abundant species in wood burning aerosols, showed a significant hygroscopic growth for particles with a diameter of 100 nm. No efflorescence was observed under the measured relative humidity, and a supersaturated condition of levoglucosan-water particles was observed. The growth factors of levoglucosan are 1.08, 1.18, 1.23, and 1.38 at relative humidity (RH) of 60, 80, 85, and 90%, respectively. The measured hygroscopic curves are in general consistent with those estimated from ideal solution theory and Uniquac Functional-Group Activity Coefficient (UNIFAC) and Conductor-Like Screening Model for Real Solvent (COSMO-RS) methods. Significant hygroscopic growth was also observed for D-glucose, whose growth factor is quite similar to that of levoglucosan. However, three model pyrolysis products of lignin (i.e., vanillic-, syringic-, and 4-hydroxybenzoic acids) did not show any hygroscopic growth under the RH conditions up to 95%. On the basis of the organic composition of wood burning aerosols, the water absorption attributed to levoglucosan in wood burning aerosols is calculated to be up to 30% of the organic mass at 90% RH. This study demonstrates that oxygenated organics emitted from biomass burning could significantly enhance the hygroscopic properties of atmospheric aerosols.

  19. Direct effect of aerosol optical properties on global dimming and brightening

    NASA Astrophysics Data System (ADS)

    Kudo, R.; Uchiyama, A.

    2011-12-01

    Surface solar radiation observed at numerous locations has decreased from the 1960s to the 1980s (Global dimming), thereafter increased (Global brightening). The dimming and brightening is considered to be due to the changes in both clouds and aerosols. Aerosols have a direct impact on the surface solar radiation by scattering and absorption. The impact is determined by three parameters: optical depth (AOD), single scattering albedo (SSA), and asymmetry factor, but the effect of asymmetry factor is rather smaller than the others. Therefore, the long-term changes in AOD and SSA are necessary to evaluate the aerosol impact on the global dimming and brightening. We have developed the method to estimate AOD and SSA from the hourly accumulated direct and diffuse irradiances measured by the ground-based broadband radiometers. In the estimation, the real part of the refractive index is fixed, and the size distribution is defined by the Junge distribution with a fixed shaping constant. Using the developed method, the measurements from 1975 to 2008 at 14 sites in Japan were analyzed. Consequently, a decrease of AOD by 0.02 and an increase of SSA by 0.2 during the period were seen. The surface solar radiation under the clear sky conditions, which was calculated from the estimated aerosol optical properties, was increased by 5% due to the changes in AOD and SSA; the influence of SSA was dominant. We also investigate the cloud impact on the surface solar radiation which was simply defined as the difference between the surface solar radiation under the cloudy sky conditions and under the clear sky conditions; the cloud impact had no statistically significant trends. The brightening in Japan may be due to the changes in aerosol optical properties, especially SSA. Our developed method can be applied to measurements at other sites around the world and would be helpful to understand the causes of the global dimming and brightening.

  20. Regional Haze from Forest Fires and San Joaquin Valley Pollution: Aerosol Properties at Yosemite National Park

    NASA Astrophysics Data System (ADS)

    Carrico, C. M.; Day, D.; Heath, J.; Lee, T.; Herckes, P.; Engling, G.; Kreidenweis, S. M.; Collett, J. L.; Bench, G.; Malm, W.

    2002-12-01

    The impact of forest fire smoke on air quality and visibility in national parks is a growing concern, particularly in light of EPA's new Regional Haze rule. The summer of 2002 proved to be a very active year for wildfires in the western U.S. with double the average acres burned. To improve understanding of smoke aerosols, an intensive campaign to measure aerosol chemical, physical, optical, and in particular hygroscopic properties, was conducted in Yosemite National Park in July-September 2002. High time resolution chemical measurements allowed speciation of major ions and carbon with 15 and 60 minute time resolution, respectively. Preliminary results show a predominant contribution of organic carbon with concentrations ranging from ~5-15 μgm-3 while major ions were dominated by sulfate, nitrate and ammonium and totaled approximately 2 μgm-3. Carbon isotopic analysis showed that during the haziest periods most carbon had a biogenic source. Soluble potassium and UV light absorption were observed to be useful indicators of smoke impact. During smoky periods, dry light scattering coefficients ranged from roughly 50-200 Mm-1, comparable to the most polluted US cities. Measurements using light scattering and diameter growth techniques both showed limited aerosol hygroscopicity. Diameter and light scattering growth factors ranged from roughly 1.05-1.2 and 1.1-1.5, respectively, at RH = 80%. Measurements of the aerosol dry size distribution during hazy periods showed a mode in the optically efficient size of several hundred nm in addition to a typical number concentration mode around 100 nm. In general, the aerosol properties at Yosemite were observed to have strong influences from smoke likely transported from massive regional wildfires as well as pollution likely from agricultural and population centers of Central California.

  1. Microwave absorption properties of composite powders with low density

    NASA Astrophysics Data System (ADS)

    Mu, Guohong; Shen, Haigen; Qiu, Jianxun; Gu, Mingyuan

    2006-12-01

    The composites of barium ferrite coated on hollow ceramic microspheres were prepared using sol-gel technique. The crystal structure, morphology and microwave absorption properties of composite powders with different weight ratio of microspheres were studied with XRD, EDS, FESEM and vector network analyzer. The results show that the microwave absorption properties of composite powders are greatly improved. The maximum microwave loss of composite powders reaches 31 dB with an amount of 50 wt.% microspheres, and its density is only about 1.80 g/cm 3. The effect of hollow ceramic microspheres on the microwave absorption property is also discussed.

  2. Photoacoustic and filter-based ambient aerosol light absorption measurements: Instrument comparisons and the role of relative humidity

    NASA Astrophysics Data System (ADS)

    Arnott, W. P.; Moosmüller, H.; Sheridan, P. J.; Ogren, J. A.; Raspet, R.; Slaton, W. V.; Hand, J. L.; Kreidenweis, S. M.; Collett, J. L.

    2003-01-01

    Ambient measurements are reported of aerosol light absorption from photoacoustic and filter-based instruments (aethalometer and a particle soot absorption photometer (PSAP)) to provide insight on the measurement science. Measurements were obtained during the Big Bend Regional Aerosol and Visibility Observational Study at the Big Bend National Park in South Texas. The aethalometer measurements of black carbon concentration at this site correlate reasonably well with photoacoustic measurements of aerosol light absorption, with a slope of 8.1 m2/g and a small offset. Light absorption at this site never exceeded 2.1 Mm-1 during the month of collocated measurements. Measurements were also obtained, as a function of controlled relative humidity between 40% and 90%, during the Photoacoustic IOP in 2000 at the Department of Energy Southern Great Plains Cloud and Radiation Testbed site (SGP). PSAP measurements of aerosol light absorption correlated very well with photoacoustic measurements, but the slope of the correlation indicated the PSAP values were larger by a factor of 1.61. The photoacoustic measurements of light absorption exhibited a systematic decrease when the RH increased beyond 70%. This apparent decrease in light absorption with RH may be due to the contribution of mass transfer to the photoacoustic signal. Model results for the limiting case of full water saturation are used to evaluate this hypothesis. A second PSAP measured the light absorption for the same humidified samples, and indicated very erratic response as the RH changed, suggesting caution when interpreting PSAP data under conditions of rapid relative humidity change.

  3. Midinfrared optical properties of petroleum oil aerosols. Final report

    SciTech Connect

    Gurton, K.P.; Bruce, C.W.

    1994-08-01

    The mass normalized absorption and extinction coefficients were measured for fog oil aerosol at 3.4 micrometers with a combined photoacoustic and transmissometer system. An extinction spectral profile was determined over a range of infrared (IR) wavelengths from 2.7 to 4.0 micrometers by an IR scanning transmissometer. The extinction spectrum was mass normalized by referencing it to the photoacoustic portion of the experiment. A corresponding Mie calculation was conducted and compared with the above measurements. Agreement is good for the most recent optical coefficients. An extrapolation of this data to other similar petroleum products such as kerosene or diesel fuel that exhibit similar bulk absorption characteristics were briefly examined.

  4. Stability properties of wines by absorption spectra

    NASA Astrophysics Data System (ADS)

    Larena, A.; Vega, J.

    1986-03-01

    The temporal evolution of absorption spectra (370-700 nm) of different spanish wines has been studied by us under the influence of air presence, and the light exposition. In particular, we have exposed the wines to a magenta light. Nevertheless, the color coordinates of wine show a little relative variation (0.1-1 %)

  5. Aerosol optical properties and mixing state of black carbon in the Pearl River Delta, China

    NASA Astrophysics Data System (ADS)

    Tan, Haobo; Liu, Li; Fan, Shaojia; Li, Fei; Yin, Yan; Cai, Mingfu; Chan, P. W.

    2016-04-01

    Aerosols contribute the largest uncertainty to the total radiative forcing estimate, and black carbon (BC) that absorbs solar radiation plays an important role in the Earth's energy budget. This study analysed the aerosol optical properties from 22 February to 18 March 2014 at the China Meteorological Administration Atmospheric Watch Network (CAWNET) station in the Pearl River Delta (PRD), China. The representative values of dry-state particle scattering coefficient (σsp), hemispheric backscattering coefficient (σhbsp), absorption coefficient (σabsp), extinction coefficient (σep), hemispheric backscattering fraction (HBF), single scattering albedo (SSA), as well as scattering Ångström exponent (α) were presented. A comparison between a polluted day and a clean day shows that the aerosol optical properties depend on particle number size distribution, weather conditions and evolution of the mixing layer. To investigate the mixing state of BC at the surface, an optical closure study of HBF between measurements and calculations based on a modified Mie model was employed for dry particles. The result shows that the mixing state of BC might be between the external mixture and the core-shell mixture. The average retrieved ratio of the externally mixed BC to the total BC mass concentration (rext-BC) was 0.58 ± 0.12, and the diurnal pattern of rext-BC can be found. Furthermore, considering that non-light-absorbing particles measured by a Volatility-Tandem Differential Mobility Analyser (V-TDMA) exist independently with core-shell and homogenously internally mixed BC particles, the calculated optical properties were just slightly different from those based on the assumption that BC exist in each particle. This would help understand the influence of the BC mixing state on aerosol optical properties and radiation budget in the PRD.

  6. Vertical Profiles of Cloud Condensation Nuclei, Condensation Nuclei, Optical Aerosol, Aerosol Optical Properties, and Aerosol Volatility Measured from Balloons

    NASA Technical Reports Server (NTRS)

    Deshler, T.; Snider, J. R.; Vali, G.

    1998-01-01

    Under the support of this grant a balloon-borne gondola containing a variety of aerosol instruments was developed and flown from Laramie, Wyoming, (41 deg N, 105 deg W) and from Lauder, New Zealand (45 deg S, 170 deg E). The gondola includes instruments to measure the concentrations of condensation nuclei (CN), cloud condensation nuclei (CCN), optically detectable aerosol (OA.) (r greater than or equal to 0.15 - 2.0 microns), and optical scattering properties using a nephelometer (lambda = 530 microns). All instruments sampled from a common inlet which was heated to 40 C on ascent and to 160 C on descent. Flights with the CN counter, OA counter, and nephelometer began in July 1994. The CCN counter was added in November 1994, and the engineering problems were solved by June 1995. Since then the flights have included all four instruments, and were completed in January 1998. Altogether there were 20 flights from Laramie, approximately 5 per year, and 2 from Lauder. Of these there were one or more engineering problems on 6 of the flights from Laramie, hence the data are somewhat limited on those 6 flights, while a complete data set was obtained from the other 14 flights. Good CCN data are available from 12 of the Laramie flights. The two flights from Lauder in January 1998 were successful for all measurements. The results from these flights, and the development of the balloon-bome CCN counter have formed the basis for five conference presentations. The heated and unheated CN and OA measurements have been used to estimate the mass fraction of the aerosol volatile, while comparisons of the nephelometer measurements were used to estimate the light scattering, associated with the volatile aerosol. These estimates were calculated for 0.5 km averages of the ascent and descent data between 2.5 km and the tropopause, near 11.5 km.

  7. A COMPARISON OF CMAQ-BASED AEROSOL PROPERTIES WITH IMPROVE, MODIS, AND AERONET DATA

    EPA Science Inventory

    We compare select aerosol Properties derived from the Community Multiscale Air Quality (CMAQ) model-simulated aerosol mass concentrations with routine data from the National Aeronautics and Space Administration (NASA) satellite-borne Moderate Resolution Imaging Spectro-radiometer...

  8. Biomass burning aerosol over the Amazon during SAMBBA: impact of chemical composition on radiative properties

    NASA Astrophysics Data System (ADS)

    Morgan, William; Allan, James; Flynn, Michael; Darbyshire, Eoghan; Hodgson, Amy; Liu, Dantong; O'shea, Sebastian; Bauguitte, Stephane; Szpek, Kate; Langridge, Justin; Johnson, Ben; Haywood, Jim; Longo, Karla; Artaxo, Paulo; Coe, Hugh

    2014-05-01

    Biomass burning represents one of the largest sources of particulate matter to the atmosphere, resulting in a significant perturbation to the Earth's radiative balance coupled with serious impacts on public health. Globally, biomass burning aerosols are thought to exert a small warming effect but with the uncertainty being 4 times greater than the central estimate. On regional scales, the impact is substantially greater, particularly in areas such as the Amazon Basin where large, intense and frequent burning occurs on an annual basis for several months. Absorption by atmospheric aerosols is underestimated by models over South America, which points to significant uncertainties relating to Black Carbon (BC) aerosol properties. Initial results from the South American Biomass Burning Analysis (SAMBBA) field experiment, which took place during September and October 2012 over Brazil on-board the UK Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 research aircraft, are presented here. Aerosol chemical composition was measured by an Aerodyne Aerosol Mass Spectrometer (AMS) and a DMT Single Particle Soot Photometer (SP2). The physical, chemical and optical properties of the aerosols across the region will be characterized in order to establish the impact of biomass burning on regional air quality, weather and climate. The aircraft sampled a range of conditions including sampling of pristine Rainforest, fresh biomass burning plumes, regional haze and elevated biomass burning layers within the free troposphere. The aircraft sampled biomass burning aerosol across the southern Amazon in the states of Rondonia and Mato Grosso, as well as in a Cerrado (Savannah-like) region in Tocantins state. This presented a range of fire conditions, both in terms of their number, intensity, vegetation-type and their combustion efficiencies. Near-source sampling of fires in Rainforest environments suggested that smouldering combustion dominated, while flaming combustion dominated

  9. Retrieval of stratospheric aerosol size distributions and integral properties from simulated lidar backscatter measurements.

    PubMed

    Yue, G K

    2000-10-20

    A new approach for retrieving aerosol properties from extinction spectra is extended to retrieve aerosol properties from lidar backscatter measurements. In this method it is assumed that aerosol properties are expressed as a linear combination of backscatters at three or fewer wavelengths commonly used in lidar measurements. The coefficients in the weighted linear combination are obtained by minimization of the retrieval error averaged for a set of testing size distributions. The formulas can be used easily by investigators to retrieve aerosol properties from lidar backscatter measurements such as the Lidar In-Space Technology Experiment and Pathfinder Instruments for Clouds and Aerosols Spaceborne Observations.

  10. Retrieval and Validation of Aerosol Optical Properties over East Asia from TANSO-Cloud and Aerosol Imager

    NASA Astrophysics Data System (ADS)

    Lee, Sanghee; Kim, Jhoon; Kim, Mijin; Choi, Myungje; Go, Sujung; Lim, HyunKwang; Ou, Mi-Lim; Goo, Tae-Young; Yokota, Tatsuya

    2015-04-01

    Aerosol is a significant component on air quality and climate change. In particular, spatial and temporal distribution of aerosol shows large variability over East Asia, thus has large effect in retrieving carbon dioxide from Greenhouse Gases Observing Satellite (GOSAT) Thermal And Near infrared Sensor for carbon Observation Fourier Transform Spectrometer (TANSO-FTS). An aerosol retrieval algorithm was developed from TANSO- Cloud and Aerosol Imager (CAI) onboard the GOSAT. The algorithm retrieves aerosol optical depth (AOD), size distribution of aerosol, and aerosol type in 0.1 degree grid resolution and surface reflectance was estimated using the clear sky composite method. To test aerosol absorptivity, the reflectance difference method was considered using channels of TANSO-CAI. In this study, the retrieved aerosol optical depth (AOD) was compared with those of Aerosol Robotic NETwork (AERONET) and MODerate resolution Imaging Sensor (MODIS) dataset from September 2011 and August 2014. Comparisons of AODs between AERONET and CAI show the reasonably good correlation with correlation coefficient of 0.77 and regression slope of 0.87 for the whole period. Moreover, those between MODIS and CAI for the same period show correlations with correlation coefficient of 0.7 ~ 0.9 and regression slope of 0.7 ~ 1.2, depending on season and comparison regions however, the largest error source in aerosol retrieval has been surface reflectance. Over ocean and some Land, surface reflectance tends to be overestimated, and thereby CAI-AOD tends to be underestimated. Based on the results with CAI algorithm developed, the algorithm is continuously improved for better performance.

  11. Aerosol optical properties at a coastal site in Hong Kong, South China: temporal features, size dependencies and source analysis

    NASA Astrophysics Data System (ADS)

    Wang, Jiaping; Ding, Aijun; Virkkula, Aki; Lee, Shuncheng; Shen, Yicheng; Chi, Xuguang; Xu, Zheng

    2016-04-01

    Hong Kong is a typical coastal city adjacent to the Pearl River Delta (PRD) region in southern China, which is one of the regions suffering from severe air pollution. Atmospheric aerosols can affect the earth's radiative balance by scattering and absorbing incoming solar radiation. Black Carbon (BC) aerosol is a particularly emphasized component due to its strong light absorption. Aerosol transported from different source areas consists of distinct size distributions, leading to different optical properties. As the byproducts of the incomplete oxidation, BC and CO both have relatively long life time, their relationship is a good indicator for distinguishing different pollutant sources. In this study, temporal variations of aerosol optical properties and concentrations of BC and CO at a coastal background station in Hong Kong were investigated. Transport characteristics and origins of aerosol were elucidated by analyzing backward Lagrangian particle dispersion modeling (LPDM) results, together with related parameters including the relationships between optical properties and particle size, BC-CO correlations, ship location data and meteorological variables. From February 2012 to September 2013 and March 2014 to February 2015, continuous in-situ measurements of light scattering and absorption coefficients, particle size distribution and concentrations of BC and CO were conducted at Hok Tsui (HT), a coastal background station on the southeast tip of Hong Kong Island (22.22°N, 114.25°E, 60 m above the sea level) with few local anthropogenic activities. Affected by the Asian monsoon, this region is dominated by continental outflow in winter and by marine inflow from the South China Sea in summer, which is an ideal station for identifying the transport characteristics of aerosol and their effects on optical properties from different anthropogenic emission sources. 7-day backward Lagrangian particle dispersion modeling was performed for source identification. Three

  12. Sensitivity of thermal infrared sounders to the chemical and micro-physical properties of UTLS secondary sulphate aerosols

    NASA Astrophysics Data System (ADS)

    Sellitto, P.; Legras, B.

    2015-08-01

    Monitoring upper tropospheric-lower stratospheric (UTLS) secondary sulphate aerosols and their chemical and micro-physical properties from satellite nadir observations is crucial to better understand their formation and evolution processes and then to estimate their impact to the UTLS chemistry, and on regional and global radiative balance. Here we present a study aimed at the evaluation of the sensitivity of thermal infrared (TIR) satellite nadir observations to the chemical composition and the size distribution of idealized UTLS sulphate aerosol layers. The extinction properties of sulphuric acid/water droplets, for different sulphuric acid mixing ratios and temperatures, are systematically analysed. The extinction coefficients are derived by means of a Mie code, using refractive indexes taken from the GEISA (Gestion et Étude des Informations Spectroscopiques Atmosphériques: Management and Study of Spectroscopic Information) spectroscopic database and log-normal size distributions with different effective radii and number concentrations. IASI (Infrared Atmospheric Sounding Interferometer) pseudo-observations are generated using forward radiative transfer calculations performed with the 4A (Automatized Atmospheric Absorption Atlas) radiative transfer model, to estimate the impact of the extinction of idealized aerosol layers, at typical UTLS conditions, on the brightness temperature spectra observed by this satellite instrument. We found a marked and typical spectral signature of these aerosol layers between 700 and 1200 cm-1, due to the absorption bands of the sulphate and bi-sulphate ions and the undissociated sulphuric acid, with the main absorption peaks at 1170 and 905 cm-1. The dependence of the aerosol spectral signature to the sulphuric acid mixing ratio, and effective number concentration and radius, as well as the role of interferring parameters like the ozone, sulphur dioxide, carbon dioxide and ash absorption, and temperature and water vapour profile

  13. Rural continental aerosol properties and processes observed during the Hohenpeissenberg Aerosol Characterization Experiment (HAZE2002)

    NASA Astrophysics Data System (ADS)

    Hock, N.; Schneider, J.; Borrmann, S.; Römpp, A.; Moortgat, G.; Franze, T.; Schauer, C.; Pöschl, U.; Plass-Dülmer, C.; Berresheim, H.

    2007-06-01

    Detailed investigations of the chemical and microphysical properties of rural continental aerosols were performed during the HAZE2002 experiment, which was conducted in May 2002 at the Meteorological Observatory Hohenpeissenberg (DWD) in Southern Germany. The online measurement data and techniques included: size-resolved chemical composition of submicron particles by aerosol mass spectrometry (AMS); total particle number concentrations and size distributions over the diameter range of 3 nm to 9 μm (CPC, SMPS, OPC); monoterpenes determined by gas chromatography- ion trap mass spectrometry; OH and H2SO4 determined by atmospheric pressure chemical ionization mass spectrometry (CIMS). Filter sampling and offline analytical techniques were used to determine: fine particle mass (PM2.5), organic, elemental and total carbon in PM2.5 (OC2.5, EC2.5, TC2.5), and selected organic compounds (dicarboxylic acids, polycyclic aromatic hydrocarbons, proteins). Overall, the non-refractory components of submicron particles detected by aerosol mass spectrometry (PM1, 6.6±5.4 μg m-3, arithmetic mean and standard deviation) accounted for ~62% of PM2.5 determined by filter gravimetry (10.6±4.7 μg m-3). The relative proportions of non-refractory submicron particle components were: 11% ammonium, 19% nitrate, 20% sulfate, and 50% organics (OM1). In spite of strongly changing meteorological conditions and absolute concentration levels of particulate matter (3-13 μg m-3 PM1), OM1 was closely correlated with PM1 (r2=0.9) indicating a near-constant ratio of non-refractory organics and inorganics. In contrast, the ratio of nitrate to sulfate was highly dependent on temperature (14-32°C) and relative humidity (20-100%), which could be explained by thermodynamic model calculations of NH3/HNO3/NH4NO3 gas-particle partitioning. From the combination of optical and other sizing techniques (OPC, AMS, SMPS), an average refractive index of 1.40-1.45 was inferred for the measured rural aerosol

  14. Evaluation of aerosol properties simulated by the high resolution global coupled chemistry-aerosol-microphysics model C-IFS-GLOMAP

    NASA Astrophysics Data System (ADS)

    Dhomse, Sandip; Mann, Graham; Carslaw, Ken; Flemming, Johannes; Morcrette, Jean-Jacques; Engelen, Richard; Remy, Samuel; Boucher, Olivier; Benduhn, Francois; Hewson, Will; Woodhouse, Matthew

    2016-04-01

    The EU Framework Programme GEMS and MACC consortium projects co-ordinated by the European Centre for Medium-range Weather Forecasts (ECMWF) have developed an operational global forecasting and reanalysis system (Composition-IFS) for atmospheric composition including greenhouse gases, reactive gases and aerosol. The current operational C-IFS system uses a mass-based aerosol model coupled to data assimilation of Aerosol Optical Depth measured by satellite (MODIS) to predict global aerosol properties. During MACC, the GLOMAP-mode aerosol microphysics scheme was added to the system, providing information on aerosol size and number for improved representation of aerosol-radiation and aerosol-cloud interactions, accounting also for simulated global variations in size distribution and internally-mixed particle composition. The IFS-GLOMAP system has recently been upgraded to couple with the sulphur cycle simulated in the online TM5 tropospheric chemistry module for global reactive gases. This C-IFS-GLOMAP system is also being upgraded to use a new "nitrate-extended" version of GLOMAP which realistically treats the size-resolved gas-particle partitioning of semi volatile gases ammonia and nitric acid. In this poster we described C-IFS-GLOMAP and present an evaluation of the global sulphate aerosol distribution simulated in this coupled aerosol-chemistry C-IFS-GLOMAP, comparing to surface observations in Europe, North America and the North Atlantic and contrasting to the fixed timescale sulphate production scheme developed in GEMS. We show that the coupling to the TM5 sulphur chemistry improves the seasonal cycle of sulphate aerosol, for example addressing a persistent wintertime sulphate high bias in northern Europe. The improved skill in simulated sulphate aerosol seasonal cycle is a pre-requisite to realistically characterise nitrate aerosol since biases in sulphate affect the amount of free ammonia available to form ammonium nitrate.

  15. Evaluations of tropospheric aerosol properties simulated by the community earth system model with a sectional aerosol microphysics scheme

    PubMed Central

    Toon, Owen B.; Bardeen, Charles G.; Mills, Michael J.; Fan, Tianyi; English, Jason M.; Neely, Ryan R.

    2015-01-01

    Abstract A sectional aerosol model (CARMA) has been developed and coupled with the Community Earth System Model (CESM1). Aerosol microphysics, radiative properties, and interactions with clouds are simulated in the size‐resolving model. The model described here uses 20 particle size bins for each aerosol component including freshly nucleated sulfate particles, as well as mixed particles containing sulfate, primary organics, black carbon, dust, and sea salt. The model also includes five types of bulk secondary organic aerosols with four volatility bins. The overall cost of CESM1‐CARMA is approximately ∼2.6 times as much computer time as the standard three‐mode aerosol model in CESM1 (CESM1‐MAM3) and twice as much computer time as the seven‐mode aerosol model in CESM1 (CESM1‐MAM7) using similar gas phase chemistry codes. Aerosol spatial‐temporal distributions are simulated and compared with a large set of observations from satellites, ground‐based measurements, and airborne field campaigns. Simulated annual average aerosol optical depths are lower than MODIS/MISR satellite observations and AERONET observations by ∼32%. This difference is within the uncertainty of the satellite observations. CESM1/CARMA reproduces sulfate aerosol mass within 8%, organic aerosol mass within 20%, and black carbon aerosol mass within 50% compared with a multiyear average of the IMPROVE/EPA data over United States, but differences vary considerably at individual locations. Other data sets show similar levels of comparison with model simulations. The model suggests that in addition to sulfate, organic aerosols also significantly contribute to aerosol mass in the tropical UTLS, which is consistent with limited data.

  16. Evaluations of tropospheric aerosol properties simulated by the community earth system model with a sectional aerosol microphysics scheme

    PubMed Central

    Toon, Owen B.; Bardeen, Charles G.; Mills, Michael J.; Fan, Tianyi; English, Jason M.; Neely, Ryan R.

    2015-01-01

    Abstract A sectional aerosol model (CARMA) has been developed and coupled with the Community Earth System Model (CESM1). Aerosol microphysics, radiative properties, and interactions with clouds are simulated in the size‐resolving model. The model described here uses 20 particle size bins for each aerosol component including freshly nucleated sulfate particles, as well as mixed particles containing sulfate, primary organics, black carbon, dust, and sea salt. The model also includes five types of bulk secondary organic aerosols with four volatility bins. The overall cost of CESM1‐CARMA is approximately ∼2.6 times as much computer time as the standard three‐mode aerosol model in CESM1 (CESM1‐MAM3) and twice as much computer time as the seven‐mode aerosol model in CESM1 (CESM1‐MAM7) using similar gas phase chemistry codes. Aerosol spatial‐temporal distributions are simulated and compared with a large set of observations from satellites, ground‐based measurements, and airborne field campaigns. Simulated annual average aerosol optical depths are lower than MODIS/MISR satellite observations and AERONET observations by ∼32%. This difference is within the uncertainty of the satellite observations. CESM1/CARMA reproduces sulfate aerosol mass within 8%, organic aerosol mass within 20%, and black carbon aerosol mass within 50% compared with a multiyear average of the IMPROVE/EPA data over United States, but differences vary considerably at individual locations. Other data sets show similar levels of comparison with model simulations. The model suggests that in addition to sulfate, organic aerosols also significantly contribute to aerosol mass in the tropical UTLS, which is consistent with limited data. PMID:27668039

  17. Particle Property Data Quality Flags for the MISR Aerosol Product

    NASA Astrophysics Data System (ADS)

    Gaitley, B. J.; Kahn, R. A.; Garay, M. J.

    2012-12-01

    The MISR instrument aboard the NASA Earth Observing System's Terra satellite has the unique capability to retrieve aerosol properties under favorable conditions. General aerosol type retrieval quality guidelines are provided in the MISR Data Quality Statement and related publications. Here we report on the steps we are taking to provide an aerosol-type data quality flag, to be provided with each individual retrieval result. Some factors affecting retrieval quality that can be assessed pre-retrieval are the number of cameras available, the range of scattering angles and surface conditions such as shallow water or seasonal coastal runoff. Factors that must be assessed post-retrieval include low values of retrieved optical depth and the number and type of mixtures successfully passing the MISR algorithm acceptance criteria. Regional monthly plots with MISR measurements binned at 0.5 degree resolution with color-coded stratification of one or more parameters is the main method for identifying locations and times where particle properties are retrieved. Individual MISR values such as mid-visible AOD, number and type of mixtures passing, number of cameras used, the range and maximum scattering angles are plotted individually or as joint distributions. Initially, thresholds and conditions are determined for each MISR parameter separately. Finally, MISR parameters are combined for a given month and region, with their thresholds, to show the overall quality of the retrieval for determining particle properties. Multi-month summaries for more than twelve years of MISR data will aid in assessing quality. Seasons and regions that regularly show poorly constrained aerosol type results are identified, as are times and places where particle property information can be used with confidence. This work is performed in part at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration and in part at the NASA

  18. Contribution of long-range transported aerosols to aerosol optical and physical properties: 3-year measurements at Gosan, Korea

    NASA Astrophysics Data System (ADS)

    Heo, J.; Kim, S. W.; Kim, J. H.; Ogren, J. A.; Yoon, S. C.

    2015-12-01

    Recently, more attentions have been paid to air quality in East Asia due to the enhanced loading of atmospheric pollutants related to rapid industrialization. Gosan Climate Observatory (GCO), Korea is regarded as an ideal site to study the transport of atmospheric pollutants because it is frequently influenced by various airmasses from China, Korea, Japan and Pacific Ocean. In order to understand aerosol optical and physical properties according to airmass transport routes, three-year (2012-2014) continuous measurements of aerosol scattering/absorption coefficient and number size distribution were analyzed, together with 48-hour backward trajectory calculations. The averaged aerosol absorption (σa) and scattering coefficient (σs) for airmasses transported from North China (NC; 36% of all trajectories) were 6.65 Mm-1 and 94.72 Mm-1 at 550 nm wavelength, respectively, which were similar to those for stagnant airmasses (ST; 22% of all trajectories; σa: 6.26 Mm-1, σs: 93.99 Mm-1). The highest values of σa (7.03 Mm-1) and σs (108.34 Mm-1) were observed when airmasses were traveled from South China (SC; 11% of all trajectories). σa and σs for airmasses from Korean Peninsula (KP; 7% of all trajectories) and Pacific Ocean (PO; 14% of all trajectories; in parenthesis) were 5.63 (2.76) Mm-1 and 73.63 (50.93) Mm-1, respectively. Compared to other airmasses, the higher values of Scattering Angstrom Exponent (SAE) for ST (1.65) is thought to be the build-up of anthropogenic fine particulate pollutants. The Absorption Angstrom Exponent (AAE) was estimated to be 1.32 for NC airmass and 1.02 for SC airmass. Over the study period, 130 days of total 557 days were identified as new particle formation and growth event (NPF) from Scanning Mobility Particle Sizer (SMPS) measurements by Cyclostationary Empirical Orthogonal Function (CSEOF) approach. Especially, 55.4% (72 days) of total 130 NPF days were found when a cold and dry airmass comes from NC after passing the frontal

  19. Optical properties and cross-sections of biological aerosols

    NASA Astrophysics Data System (ADS)

    Thrush, E.; Brown, D. M.; Salciccioli, N.; Gomes, J.; Brown, A.; Siegrist, K.; Thomas, M. E.; Boggs, N. T.; Carter, C. C.

    2010-04-01

    There is an urgent need to develop standoff sensing of biological agents in aerosolized clouds. In support of the Joint Biological Standoff Detection System (JBSDS) program, lidar systems have been a dominant technology and have shown significant capability in field tests conducted in the Joint Ambient Breeze Tunnel (JABT) at Dugway Proving Ground (DPG). The release of biological agents in the open air is forbidden. Therefore, indirect methods must be developed to determine agent cross-sections in order to validate sensor against biological agents. A method has been developed that begins with laboratory measurements of thin films and liquid suspensions of biological material to obtain the complex index of refraction from the ultraviolet (UV) to the long wave infrared (LWIR). Using that result and the aerosols' particle size distribution as inputs to Mie calculations yields the backscatter and extinction cross-sections as a function of wavelength. Recent efforts to model field measurements from the UV to the IR have been successful. Measurements with aerodynamic and geometric particle sizers show evidence of particle clustering. Backscatter simulations of these aerosols show these clustered particles dominate the aerosol backscatter and depolarization signals. In addition, these large particles create spectral signatures in the backscatter signal due to material absorption. Spectral signatures from the UV to the IR have been observed in simulations of field releases. This method has been demonstrated for a variety of biological simulant materials such as Ovalbumin (OV), Erwinia (EH), Bacillus atrophaeus (BG) and male specific bacteriophage (MS2). These spectral signatures may offer new methods for biological discrimination for both stand-off sensing and point detection systems.

  20. Studing Taklamakan aerosol properties with Lidar (STAPL)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    By now, the global impacts of atmospheric dust have been well-established. Nevertheless, relevant properties such as size distribution, depolarization ratio, and even single-scattering albedo have been shown to vary substantially between dust producing regions and are also strongly dependent on the ...

  1. In Situ Measurements of Aerosol Mass Concentration and Spectral Absorption at Three Location in and Around Mexico City

    NASA Astrophysics Data System (ADS)

    Chaudhry, Z.; Martins, V.; Li, Z.

    2006-12-01

    As a result of population growth and increasing industrialization, air pollution in heavily populated urban areas is one of the central environmental problems of the century. As a part of the MILAGRO (Megacity Initiative: Local and Global Research Observations) study, Nuclepore filters were collected in two size ranges (PM10 and PM2.5) at 12 hour intervals at three location in Mexico during March, 2006. Sampling stations were located at the Instituto Mexicano del Petroleo (T0), at the Rancho La Bisnago in the State of Hidalgo (T2) and along the Gulf Coast in Tampico (Tam). Each filter was analyzed for mass concentration, aerosol scattering and absorption efficiencies. Mass concentrations at T0 ranged from 47 to 179 μg/m3 for PM10 with an average concentration of 96 μg/m3, and from 20 to 93 μg/m3 for PM2.5 with an average concentration of 41 μg/m3. Mass concentrations at T2 ranged from 12 to 154 μg/m3 for PM10 with an average concentration of 51 μg/m3, and from 7 to 50 μg/m3 for PM2.5 with an average concentration of 25 μg/m3. Mass concentrations at Tam ranged from 34 to 80 μg/m3 for PM10 with an average concentration of 52 μg/m3, and from 8 to 23 μg/m3 for PM2.5 with an average concentration of 13 μg/m3. While some of the extreme values are likely linked to local emissions, regional air pollution episodes also played important roles. Each of the sampling stations experienced a unique atmospheric condition. The site at T0 was influenced by urban air pollution and dust storms, the site at T2 was significantly less affected by air pollution but more affected by regional dust storms and local dust devils while Tam was influenced by air pollution, dust storms and the natural marine environment. The spectral mass absorption efficiency was measured from 350 to 2500 nm and shows large differences between the absorption properties of soil dust, black carbon, and organic aerosols. The strong spectral differences observed can be related to differences in

  2. Analysis of the sensitivity of thermal infrared nadir satellite observations to the chemical and micro-physical properties of upper tropospheric-lower stratospheric sulphate aerosols

    NASA Astrophysics Data System (ADS)

    Sellitto, Pasquale; Sèze, Geneviève; Legras, Bernard

    2015-04-01

    Secondary sulphate aerosols are the predominant typology of aerosols in the upper troposphere/lower stratosphere (UTLS), and can have an important impact on radiative transfer and climate, cirrus formation and chemistry in the UTLS. Despite their importance, the satellite observation at the regional scale of sulphate aerosols in the UTLS is limited. In this work, we address the sensitivity of the thermal infrared satellite observations to secondary sulphate aerosols in the UTLS. The absorption properties of sulphuric acid/water droplets, for different sulphuric acid mixing ratios and temperatures, are systematically analysed. The absorption coefficients are derived by means of a Mie code, using refractive indexes taken from the GEISA (Gestion et Etude des Informations Spectroscopiques Atmosphériques : Management and Study of Spectroscopic Information) spectroscopic database and log-normal size distributions with different effective radii and number concentrations. IASI (Infrared Atmospheric Sounding Interferometer) and SEVIRI (Spinning Enhanced Visible and Infrared Imager) pseudo-observations are generated using forward radiative transfer calculations performed with the 4A (Automatized Atmospheric Absorption Atlas) radiative transfer model, to estimate the impact of the absorption of idealized aerosol layers, at typical UTLS conditions, on the radiance spectra observed by these simulated satellite instruments. We found a marked spectral signature of these aerosol layers between 700 and 1200 cm-1, due to the absorption bands of the sulphate and bi-sulphate ions and the undissociated sulphuric acid, with absorption peaks at 1170 and 905 cm-1. Micro-windows with a sensitivity to chemical and micro-physical properties of the sulphate aerosol layer are identified, and the role of interfering species, and temperature and water vapour profile is discussed.

  3. Optical properties and aging of light-absorbing secondary organic aerosol

    DOE PAGES

    Liu, Jiumeng; Lin, Peng; Laskin, Alexander; Laskin, Julia; Kathmann, Shawn M.; Wise, Matthew; Caylor, Ryan; Imholt, Felisha; Selimovic, Vanessa; Shilling, John E.

    2016-10-14

    The light-absorbing organic aerosol (OA) commonly referred to as “brown carbon” (BrC) has attracted considerable attention in recent years because of its potential to affect atmospheric radiation balance, especially in the ultraviolet region and thus impact photochemical processes. A growing amount of data has indicated that BrC is prevalent in the atmosphere, which has motivated numerous laboratory and field studies; however, our understanding of the relationship between the chemical composition and optical properties of BrC remains limited. We conducted chamber experiments to investigate the effect of various volatile organic carbon (VOC) precursors, NOx concentrations, photolysis time, and relative humidity (RH) on the light absorptionmore » of selected secondary organic aerosols (SOA). Light absorption of chamber-generated SOA samples, especially aromatic SOA, was found to increase with NOx concentration, at moderate RH, and for the shortest photolysis aging times. The highest mass absorption coefficient (MAC) value is observed from toluene SOA products formed under high-NOx conditions at moderate RH, in which nitro-aromatics were previously identified as the major light-absorbing compounds. BrC light absorption is observed to decrease with photolysis time, correlated with a decline of the organic nitrate fraction of SOA. SOA formed from mixtures of aromatics and isoprene absorb less visible (Vis) and ultraviolet (UV) light than SOA formed from aromatic precursors alone on a mass basis. However, the mixed SOA absorption was underestimated when optical properties were predicted using a two-product SOA formation model, as done in many current climate models. Further investigation, including analysis on detailed mechanisms, are required to explain the discrepancy.« less

  4. Backscattering measurements of atmospheric aerosols at CO2 laser wavelengths: implications of aerosol spectral structure on differential-absorption lidar retrievals of molecular species.

    PubMed

    Ben-David, A

    1999-04-20

    The volume backscattering coefficients of atmospheric aerosol were measured with a tunable CO2 lidar system at various wavelengths in Utah (a desert environment) along a horizontal path a few meters above the ground. In deducing the aerosol backscattering, a deconvolution (to remove the smearing effect of the long CO2 lidar pulse and the lidar limited bandwidth) and a constrained-slope method were employed. The spectral shape beta(lambda) was similar for all the 13 measurements during a 3-day period. A mean aerosol backscattering-wavelength dependence beta(lambda) was computed from the measurements and used to estimate the error Delta(CL) (concentration-path-length product) in differential-absorption lidar measurements for various gases caused by the systematic aerosol differential backscattering and the error that is due to fluctuations in the aerosol backscattering. The water-vapor concentration-path-length product CL and the average concentration C = /L for a path length L computed from the range-resolved lidar measurements is consistently in good agreement with the water-vapor concentration measured by a meteorological station. However, I was unable to deduce, reliably, the range-resolved water-vapor concentration C(r), which is the derivative of the range-dependent product CL, because of the effect of residual noise caused mainly by errors in the deconvolved lidar measurements.

  5. Size distribution and optical properties of mineral dust aerosols transported in the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Denjean, C.; Cassola, F.; Mazzino, A.; Triquet, S.; Chevaillier, S.; Grand, N.; Bourrianne, T.; Momboisse, G.; Sellegri, K.; Schwarzenbock, A.; Freney, E.; Mallet, M.; Formenti, P.

    2015-08-01

    This study presents in situ aircraft measurements of Saharan mineral dust transported over the western Mediterranean basin in June-July 2013 during the ChArMEx/ADRIMED (the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) airborne campaign. Dust events differing in terms of source region (Algeria, Tunisia and Morocco), time of tranport (1-5 days) and height of transport were sampled. Mineral dust were transported above the marine boundary layer, which conversely was dominated by pollution and marine aerosols. The dust vertical structure was extremely variable and characterized by either a single layer or a more complex and stratified structure with layers originating from different source regions. Mixing of mineral dust with pollution particles was observed depending on the height of transport of the dust layers. Dust layers carried higher concentration of pollution particles at intermediate altitude (1-3 km) than at elevated altitude (> 3 km), resulting in scattering Angstrom exponent up to 2.2 within the intermediate altitude. However, the optical properties of the dust plumes remained practically unchanged with respect to values previously measured over source regions, regardless of the altitude. Moderate light absorption of the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00 ± 0.04. Concurrent calculations from the aerosol chemical composition revealed a negligible contribution of pollution particles to the absorption properties of the dust plumes that was due to a low contribution of refractory black carbon in regards to the fraction of dust and sulfate particles. This suggests that, even in the presence of moderate pollution, likely a persistent feature in the Mediterranean, the optical properties of the dust plumes could be assimilated to those of native dust in radiative transfer simulations, modeling studies and

  6. Size distribution and optical properties of mineral dust aerosols transported in the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Denjean, C.; Cassola, F.; Mazzino, A.; Triquet, S.; Chevaillier, S.; Grand, N.; Bourrianne, T.; Momboisse, G.; Sellegri, K.; Schwarzenbock, A.; Freney, E.; Mallet, M.; Formenti, P.

    2016-02-01

    This study presents in situ aircraft measurements of Saharan mineral dust transported over the western Mediterranean basin in June-July 2013 during the ChArMEx/ADRIMED (the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) airborne campaign. Dust events differing in terms of source region (Algeria, Tunisia and Morocco), time of transport (1-5 days) and height of transport were sampled. Mineral dust were transported above the marine boundary layer, which conversely was dominated by pollution and marine aerosols. The dust vertical structure was extremely variable and characterized by either a single layer or a more complex and stratified structure with layers originating from different source regions. Mixing of mineral dust with pollution particles was observed depending on the height of transport of the dust layers. Dust layers carried a higher concentration of pollution particles below 3 km above sea level (a.s.l.) than above 3 km a.s.l., resulting in a scattering Ångström exponent up to 2.2 below 3 km a.s.l. However, the optical properties of the dust plumes remained practically unchanged with respect to values previously measured over source regions, regardless of the altitude. Moderate absorption of light by the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00. Concurrent calculations from the aerosol chemical composition revealed a negligible contribution of pollution particles to the absorption properties of the dust plumes that was due to a low contribution of refractory black carbon in regards to the fraction of dust and sulfate particles. This suggests that, even in the presence of moderate pollution, likely a persistent feature in the Mediterranean, the optical properties of the dust plumes could be assumed similar to those of native dust in radiative transfer simulations, modelling studies and satellite retrievals

  7. Fractal morphology of black carbon aerosol enhances absorption in the thermal infrared wavelengths.

    PubMed

    Heinson, William R; Chakrabarty, Rajan K

    2016-02-15

    In this Letter, we numerically calculate the mass absorption cross sections (MACs) of black carbon fractal aggregates in the thermal infrared solar spectrum. Compared to equivalent-size spheres, the MAC values of aggregates show a percent enhancement of ≈150 and 400 at small and large length scales, respectively. The absorption properties of aggregates with size parameters >1 surprisingly continued to remain in the Rayleigh optics regime. We explain this phenomenon using the Maxwell-Garnett effective medium theory and the concept of phase shift parameter. PMID:26872194

  8. Rural continental aerosol properties and processes observed during the Hohenpeissenberg Aerosol Characterization Experiment (HAZE2002)

    NASA Astrophysics Data System (ADS)

    Hock, N.; Schneider, J.; Borrmann, S.; Römpp, A.; Moortgat, G.; Franze, T.; Schauer, C.; Pöschl, U.; Plass-Dülmer, C.; Berresheim, H.

    2008-02-01

    Detailed investigations of the chemical and microphysical properties of rural continental aerosols were performed during the HAZE2002 experiment, which was conducted in May 2002 at the Meteorological Observatory Hohenpeissenberg (DWD) in Southern Germany. Online measurements included: Size-resolved chemical composition of submicron particles; total particle number concentrations and size distributions over the diameter range of 3 nm to 9 μm; gas-phase concentration of monoterpenes, CO, O3, OH, and H2SO4. Filter sampling and offline analytical techniques were used to determine: Fine particle mass (PM2.5), organic, elemental and total carbon in PM2.5 (OC2.5, EC2.5, TC2.5), and selected organic compounds (dicarboxylic acids, polycyclic aromatic hydrocarbons, proteins). Overall, the non-refractory components of submicron particles detected by aerosol mass spectrometry (PM1, 6.6±5.4 μg m-3, arithmetic mean and standard deviation) accounted for ~62% of PM2.5 determined by filter gravimetry (10.6±4.7 μg m-3). The relative proportions of non-refractory submicron particle components were: (23±39)% ammonium nitrate, (27±23)% ammonium sulfate, and (50±40)% organics (OM1). OM1 was closely correlated with PM1 (r2=0.9) indicating a near-constant ratio of non-refractory organics and inorganics. The average ratio of OM1 to OC2.5 was 2.1±1.4, indicating a high proportion of heteroelements in the organic fraction of the sampled rural aerosol. This is consistent with the high ratio of oxygenated organic aerosol (OOA) over hydrocarbon-like organic aerosol (HOA) inferred from the AMS results (4:1), and also with the high abundance of proteins (~3%) indicating a high proportion of primary biological material (~30%) in PM2.5. This finding was confirmed by low abundance of PAHs (<1 ng m-3) and EC (<1 μg m-3) in PM2.5 and detection of several secondary organic aerosol compounds (dicarboxylic acids) and their precursors (monoterpenes). New particle formation was observed almost

  9. Evaluation of Aerosol Properties in GCMs using Satellite Measurements

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Jiang, J. H.; Su, H.; Zhang, H.

    2015-12-01

    Atmospheric aerosols from natural or anthropogenic sources have profound impacts on the regional and global climate. Currently the radiative forcing of aerosols predicted by global climate models remains highly uncertain, representing the largest uncertainty in climate predictions. The uncertainty mainly arises from the complicated aerosol chemical and physical properties, coarse emission inventories for pre-cursor gases as well as unrealistic representations of aerosol activation and cloud processing in global climate models. In this study, we will utilize multiple satellite measurements including MODIS, MISR and CALIPSO to quantitatively evaluate aerosol simulations from climate models. Our analyses show that the global means in AOD climatology from NCAR CAM5 and GFDL AM3 simulations are comparable with satellite measurements. However, the overall correlation coefficient between the AOD spatial patterns from CAM5 and satellite is only 0.4. Moreover, at finer scales, the magnitude of AOD in CAM5 is much lower than satellite measurements for most of the non-dust regions, especially over East Asia. GFDL AM3 shows better AOD simulations over East Asia. The underestimated AOD over remote maritime areas in CAM5 was attributed to the unrealistic wet removal processes in convective clouds of CAM5. Over continents, biases on AOD could stem from underestimations in the emissions inventory and unresolved sub-grid variations of relative humidity due to the model's coarse resolution. Uncertainty from emission inventory over developing countries in East Asia will be assessed using the newly updated Regional Emission inventory in Asia (REAS) and Multi-resolution Emission Inventory in China (MEIC) in the model simulations.

  10. Far-IR Absorption Features of Titan Aerosol Analogs Produced from Aromatic Precursors

    NASA Astrophysics Data System (ADS)

    Sebree, Joshua; Trainer, M. G.; Anderson, C. M.; Loeffler, M. J.

    2012-10-01

    The arrival of the Cassini spacecraft in orbit around Saturn has led to the discovery of benzene (C6H6) at ppm levels, as well as large positive ions in Titan’s atmosphere, tentatively identified as polycyclic aromatic hydrocarbons (PAHs).[1] The presence of aromatic molecules, which are photolytically active in the ultraviolet, may be an important part of the formation of aerosol particles in Titan’s haze layers, even at these low concentrations. To date, there have been no laboratory experiments in the literature exploring this area of study. The analysis of data from the Composite Infrared Spectrometer (CIRS) on-board Cassini has recently uncovered a broad emission feature centered at 140 cm-1 in the far-IR that is unique to the aerosol layers of Titan’s atmosphere.[2] Current optical constants from laboratory-generated aerosol analogs have been unable to reproduce this feature.[3,4] From the broadness of this feature, we speculate that the emission is a blended composite of low-energy vibrations of large molecules such as PAHs and their nitrogen containing counterparts, polycyclic aromatic nitrogen heterocycles (PANHs). We hypothesize that the inclusion of trace amounts of aromatic precursors will aid in the production of these large structures in the laboratory-generated aerosols. In this study, we perform UV irradiation of several aromatic precursors, both with and without nitrogen heteroatoms, to understand their influence on the observable characteristics of the aerosol. Measured optical and chemical properties will be compared to those formed from CH4/N2 mixtures [5,6] as well as to those from Cassini observations. [1] Waite, J. H., et al. (2007) Science 316 870-875. [2] Anderson, C.M, et al. (2011) Icarus 212 762-778. [3] Khare, B.N., et al. (1984) Icarus 60 127-137. [4] Imanaka, H., et al. (2012) Icarus 218 247-261. [5] Trainer, M.G., et al. (2006) PNAS 103 18035-18042. [6] Trainer, M.G., et al. (2012) Astrobiology 12 315-326.

  11. Vertical Profile of Aerosol Properties at Pico Mountain, Azores

    NASA Astrophysics Data System (ADS)

    Wright, K.; Mazzoleni, C.; Mazzoleni, L. R.; Dzepina, K.; Hueber, J.; China, S.; Sharma, N.

    2013-12-01

    of aerosol properties in a marine environment from the boundary layer to the free troposphere. The analysis of these data will help us understand the role of aerosol aging, vertical transport and distribution in a marine environment.

  12. Star Photometry for the Characterization of Columnar Aerosol Properties

    NASA Astrophysics Data System (ADS)

    Perez-Ramirez, D.; Lyamani, H.; Olmo Reyes, F. J.; Alados-Arboledas, L.; Whiteman, D. N.; Aceituno, J.

    2015-12-01

    Knowledge of columnar aerosol particles at nighttime is essential to completely understand aerosol dynamics and so will largely improve aerosol models. However, the current knowledge columnar nighttime aerosol is poor due to the lack of continuous measurements partly associated with previous technological limitations. Here we present the development, set up, calibration and data quality algorithms for the star photometer at the station of Granada (37.16 N, 3.60 W, 680 m a.s.l.) in Spain. The main advantage of this instrument is that make uses of a CCD camera as detector allowing direct star flux measurements. Filters center at 380, 440, 500, 670, 880 and 1020 nm allows spectral aerosol optical depth (AOD) measurements. Among all the stars, only those that are isolated and possess constant extratarrestial flux are considered. Two methods for the calibration of the system at high mountain places are presented. The first one consists of doing a Langley calibration of a selected star together with measurements of other stars. From the Langley calibration, we transferred AOD and get the calibration constants for other stars. The second method is the Astronomical Langley Method that consists of dividing the measurements by the optical air mass and so more stable calibration constant are obtained. On the other hand, the atmospheric turbulence is important for very short exposure times (< 1 s) and so uncertainties in AOD are of ±0.02 for λ < 800nm and ±0.01 for λ > 800nm. The instrument operated continuously for more than four consecutive years and so a large database was created. Cloud screening and data quality algorithms following AERONET inheritance were developed. Basically, moving averages are applied with different temporal-windows combined with a procedure to detect outliers. On the other hand, with quality data guaranteed the analysis of day-to-night columnar aerosol properties is presented. Mean AOD(440 nm) (0.18 ± 0.10 and 0.19 ± 0.11 for daytime and

  13. Technical Note: Evaluation of the WRF-Chem "Aerosol Chemical to Aerosol Optical Properties" Module using data from the MILAGRO campaign

    SciTech Connect

    Barnard, James C.; Fast, Jerome D.; Paredes-Miranda, Guadalupe L.; Arnott, W. P.; Laskin, Alexander

    2010-08-09

    A comparison between observed aerosol optical properties from the MILAGRO field campaign, which took place in the Mexico City Metropolitan Area (MCMA) during March 2006, and values simulated by the Weather Research and Forecasting model (WRF-Chem) model, reveals large differences. To help identify the source of the discrepancies, data from the MILAGRO campaign are used to evaluate the "aerosol chemical to aerosol optical properties" module implemented in the full chemistry version of the WRF-Chem model. The evaluation uses measurements of aerosol size distributions and chemical properties obtained at the MILAGRO T1 site. These observations are fed to the module, which makes predictions of various aerosol optical properties, including the scattering coefficient, Bscat; the absorption coefficient, Babs; and the single-scattering albedo, v0; all as a function of time. This simulation is compared with independent measurements obtained from a photoacoustic spectrometer (PAS) at a wavelength of 870 nm. Because of line losses and other factors, only "fine mode" aerosols with aerodynamic diameters less than 2.5 mm are considered here. Over a 10-day period, the simulations of hour-by-hour variations of Bscat are not satisfactory, but simulations of Babs and v0 are considerably better. When averaged over the 10-day period, the computed and observed optical properties agree within the uncertainty limits of the measurements and simulations. Specifically, the observed and calculated values are, respectively: (1) Bscat, 34.1 ± 5.1 Mm-1 versus 30.4 ± 4.3 Mm-1; (2) Babs, 9.7 ± 1.0 Mm-1 versus 11.7 ± 1.5 Mm-1; and (3) v0, 0.78 ± 0.04 and 0.74 ± 0.03. The discrepancies in values of v0 simulated by the full WRF-Chem model thus cannot be attributed to the "aerosol chemistry to optics" module. The discrepancy is more likely due, in part, to poor characterization of emissions near the T1 site, particularly black carbon emissions.

  14. Excellent microwave absorption property of Graphene-coated Fe nanocomposites

    PubMed Central

    Zhao, Xingchen; Zhang, Zhengming; Wang, Liaoyu; Xi, Kai; Cao, Qingqi; Wang, Dunhui; Yang, Yi; Du, Youwei

    2013-01-01

    Graphene has evoked extensive interests for its abundant physical properties and potential applications. It is reported that the interfacial electronic interaction between metal and graphene would give rise to charge transfer and change the electronic properties of graphene, leading to some novel electrical and magnetic properties in metal-graphene heterostructure. In addition, large specific surface area, low density and high chemical stability make graphene act as an ideal coating material. Taking full advantage of the aforementioned features of graphene, we synthesized graphene-coated Fe nanocomposites for the first time and investigated their microwave absorption properties. Due to the charge transfer at Fe-graphene interface in Fe/G, the nanocomposites show distinct dielectric properties, which result in excellent microwave absorption performance in a wide frequency range. This work provides a novel approach for exploring high-performance microwave absorption material as well as expands the application field of graphene-based materials. PMID:24305606

  15. Polycyclic aromatic hydrocarbons in biomass-burning emissions and their contribution to light absorption and aerosol toxicity.

    PubMed

    Samburova, Vera; Connolly, Jessica; Gyawali, Madhu; Yatavelli, Reddy L N; Watts, Adam C; Chakrabarty, Rajan K; Zielinska, Barbara; Moosmüller, Hans; Khlystov, Andrey

    2016-10-15

    In recent years, brown carbon (BrC) has been shown to be an important contributor to light absorption by biomass-burning atmospheric aerosols in the blue and near-ultraviolet (UV) part of the solar spectrum. Emission factors and optical properties of 113 polycyclic aromatic hydrocarbons (PAHs) were determined for combustion of five globally important fuels: Alaskan, Siberian, and Florida swamp peat, cheatgrass (Bromus tectorum), and ponderosa pine (Pinus ponderosa) needles. The emission factors of total analyzed PAHs were between 1.9±0.43.0±0.6 and 9.6±1.2-42.2±5.4mgPAHkg(-1)fuel for particle- and gas phase, respectively. Spectrophotometric analysis of the identified PAHs showed that perinaphthenone, methylpyrenes, and pyrene contributed the most to the total PAH light absorption with 17.2%, 3.3 to 10.5%, and 7.6% of the total particle-phase PAH absorptivity averaged over analyzed emissions from the fuels. In the gas phase, the top three PAH contributors to BrC were acenaphthylene (32.6%), anthracene (8.2%), and 2,4,5-trimethylnaphthalene (8.0%). Overall, the identified PAHs were responsible for 0.087-0.16% (0.13% on average) and 0.033-0.15% (0.11% on average) of the total light absorption by dichloromethane-acetone extracts of particle and gas emissions, respectively. Toxic equivalency factor (TEF) analysis of 16 PAHs prioritized by the United States Environmental Protection Agency (EPA) showed that benzo(a)pyrene contributed the most to the PAH carcinogenic potency of particle phase emissions (61.8-67.4% to the total carcinogenic potency of Σ16EPA PAHs), while naphthalene played the major role in carcinogenicity of the gas phase PAHs in the biomass-burning emission analyzed here (35.4-46.0% to the total carcinogenic potency of Σ16EPA PAHs). The 16 EPA-prioritized PAHs contributed only 22.1±6.2% to total particle and 23.4±11% to total gas phase PAH mass, thus toxic properties of biomass-burning PAH emissions are most likely underestimated.

  16. Polycyclic aromatic hydrocarbons in biomass-burning emissions and their contribution to light absorption and aerosol toxicity.

    PubMed

    Samburova, Vera; Connolly, Jessica; Gyawali, Madhu; Yatavelli, Reddy L N; Watts, Adam C; Chakrabarty, Rajan K; Zielinska, Barbara; Moosmüller, Hans; Khlystov, Andrey

    2016-10-15

    In recent years, brown carbon (BrC) has been shown to be an important contributor to light absorption by biomass-burning atmospheric aerosols in the blue and near-ultraviolet (UV) part of the solar spectrum. Emission factors and optical properties of 113 polycyclic aromatic hydrocarbons (PAHs) were determined for combustion of five globally important fuels: Alaskan, Siberian, and Florida swamp peat, cheatgrass (Bromus tectorum), and ponderosa pine (Pinus ponderosa) needles. The emission factors of total analyzed PAHs were between 1.9±0.43.0±0.6 and 9.6±1.2-42.2±5.4mgPAHkg(-1)fuel for particle- and gas phase, respectively. Spectrophotometric analysis of the identified PAHs showed that perinaphthenone, methylpyrenes, and pyrene contributed the most to the total PAH light absorption with 17.2%, 3.3 to 10.5%, and 7.6% of the total particle-phase PAH absorptivity averaged over analyzed emissions from the fuels. In the gas phase, the top three PAH contributors to BrC were acenaphthylene (32.6%), anthracene (8.2%), and 2,4,5-trimethylnaphthalene (8.0%). Overall, the identified PAHs were responsible for 0.087-0.16% (0.13% on average) and 0.033-0.15% (0.11% on average) of the total light absorption by dichloromethane-acetone extracts of particle and gas emissions, respectively. Toxic equivalency factor (TEF) analysis of 16 PAHs prioritized by the United States Environmental Protection Agency (EPA) showed that benzo(a)pyrene contributed the most to the PAH carcinogenic potency of particle phase emissions (61.8-67.4% to the total carcinogenic potency of Σ16EPA PAHs), while naphthalene played the major role in carcinogenicity of the gas phase PAHs in the biomass-burning emission analyzed here (35.4-46.0% to the total carcinogenic potency of Σ16EPA PAHs). The 16 EPA-prioritized PAHs contributed only 22.1±6.2% to total particle and 23.4±11% to total gas phase PAH mass, thus toxic properties of biomass-burning PAH emissions are most likely underestimated. PMID:27304373

  17. Aerosol Optical Properties During The SAMUM-2 Experiment

    NASA Astrophysics Data System (ADS)

    Toledano, C.; Freudenthaler, V.; Gross, S.; Seefeldner, M.; Gasteiger, J.; Garhammer, M.; Esselborn, M.; Wiegner, M.; Koepke, P.

    2009-03-01

    A field campaign of the Saharan Mineral Dust Experiment (SAMUM-2) took place in the Cape Verde islands in January-February 2008, to investigate the properties of long-range transported dust over the Atlantic. The Meteorological Institute of the University of Munich deployed a set of active and passive remote sensing instruments: one sun photometer, for the measurement of the direct sun irradiance and sky radiances; a broad-band UV radiometer; and 2 tropospheric lidar systems. The measurements were made in close cooperation with the other participating groups. During the measurement period the aerosol scenario over Cape Verde mostly consisted of a dust layer below 2 km and a smoke layer above 2 km height. The Saharan dust arrived in the site from the NE, whereas the smoke originated in the African equatorial region is transported from the SE. The aerosol load was also very variable over this area, with AOD (500 nm) ranging from 0.04 to 0.74. The optical properties of the layers are shown: extinction and particle depolarization ratio profiles at 3 wavelengths, as well as aerosol optical depth (in the range 340-1550 nm), Ångström exponent, size distribution and single scattering albedo.

  18. The influence of meteoric smoke particles on stratospheric aerosol properties

    NASA Astrophysics Data System (ADS)

    Mann, Graham; Brooke, James; Dhomse, Sandip; Plane, John; Feng, Wuhu; Neely, Ryan; Bardeen, Chuck; Bellouin, Nicolas; Dalvi, Mohit; Johnson, Colin; Abraham, Luke

    2016-04-01

    The ablation of metors in the thermosphere and mesosphere introduces a signficant source of particulate matter into the polar upper stratosphere. These meteoric smoke particles (MSP) initially form at nanometre sizes but in the stratosphere have grown to larger sizes (tens of nanometres) following coagulation. The presence of these smoke particles may represent a significant mechanism for the nucleation of polar stratospheric clouds and are also known to influence the properties of the stratospheric aerosol or Junge layer. In this presentation we present findings from experiments to investigate the influence of the MSP on the Junge layer, carried out with the UM-UKCA composition-climate model. The UM-UKCA model is a high-top (up to 80km) version of the general circulation model with well-resolved stratospheric dynamics, includes the aerosol microphysics module GLOMAP and has interactive sulphur chemistry suitable for the stratosphere and troposphere (Dhomse et al., 2014). We have recently added to UM-UKCA a source of meteoric smoke particles, based on prescribing the variation of the smoke particles from previous simulations with the Whole Atmosphere Community Climate Model (WACCM). In UM-UKCA, the MSP particles are transported within the GLOMAP aerosol framework, alongside interactive stratospheric sulphuric acid aerosol. For the experiments presented here, we have activated the interaction between the MSP and the stratospheric sulphuric acid aerosol. The MSP provide an important sink term for the gas phase sulphuric acid simulated in the model, with subsequent effects on the formation, growth and temporal evolution of stratospheric sulphuric acid aerosol particles. By comparing simulations with and without the MSP-sulphur interactions we quantify the influence of the meteoric smoke on the properties of volcanically-quiescent Junge layer. We also investigate the extent to which the MSP may modulate the effects from SO2 injected into the stratosphere from volcanic

  19. Constraining Black Carbon Aerosol over Asia using OMI Aerosol Absorption Optical Depth and the Adjoint of GEOS-Chem

    NASA Technical Reports Server (NTRS)

    Zhang, Li; Henze, David K.; Grell, Georg A.; Carmichael. Gregory R.; Bousserez, Nicolas; Zhang, Qiang; Torres, Omar; Ahn, Changwoo; Lu, Zifeng; Cao, Junji; Mao, Yuhao

    2015-01-01

    Accurate estimates of the emissions and distribution of black carbon (BC) in the region referred to here as Southeastern Asia (70degE-l50degE, 11degS-55degN) are critical to studies of the atmospheric environment and climate change. Analysis of modeled BC concentrations compared to in situ observations indicates levels are underestimated over most of Southeast Asia when using any of four different emission inventories. We thus attempt to reduce uncertainties in BC emissions and improve BC model simulations by developing top-down, spatially resolved, estimates of BC emissions through assimilation of OMI observations of aerosol absorption optical depth (AAOD) with the GEOS-Chem model and its adjoint for April and October of 2006. Overwhelming enhancements, up to 500%, in anthropogenic BC emissions are shown after optimization over broad areas of Southeast Asia in April. In October, the optimization of anthropogenic emissions yields a slight reduction (1-5%) over India and parts of southern China, while emissions increase by 10-50% over eastern China. Observational data from in situ measurements and AERONET observations are used to evaluate the BC inversions and assess the bias between OMI and AERONET AAOD. Low biases in BC concentrations are improved or corrected in most eastern and central sites over China after optimization, while the constrained model still underestimates concentrations in Indian sites in both April and October, possibly as a. consequence of low prior emissions. Model resolution errors may contribute up to a factor of 2.5 to the underestimate of surface BC concentrations over northern India. We also compare the optimized results using different anthropogenic emission inventories and discuss the sensitivity of top-down constraints on anthropogenic emissions with respect to biomass burning emissions. In addition, the impacts of brown carbon, the formulation of the observation operator, and different a priori constraints on the optimization are

  20. Ice Nucleation Properties of Amospherically Aged Biomass Burning Aerosol

    NASA Astrophysics Data System (ADS)

    Polen, M.; Lawlis, E.; Sullivan, R. C.

    2015-12-01

    Biomass burning can sometimes emit surprisingly active ice nucleating particles, though these emissions are not at all consistent between biomass fuel sources and burns. Soot from biomass combustion has been attributed to some but not all of the ice nucleating potential of biomass burning aerosol (BBA), while fossil fuel combustion soot emits very weak ice nucleants. The causes of the sometimes significant but variable ice nucleating ability of BBA are still largely unknown. BBA experiences significant atmospheric aging as the plume evolves and mixes with background air, yet almost no reports exploring the effects of atmospheric aging on the freezing properties of BBA have been made. We have performed some of the first experiments to determine the effects of simulated atmospheric aging on these ice nucleation properties, using a chamber reactor. The fresh and aged BBA was collected for subsequent droplet freezing array analysis using an impinger sampler to collect aerosol in water, and by deposition onto substrates in a MOUDI sampler. Droplets containing the chamber particles were then suspended in oil on a cold plate for freezing temperature spectrum measurement. Aging of Sawgrass flaming-phase combustion BBA by exposure to hydroxyl radicals (from H2O2 photolysis) enhanced the ice nucleation ability, observed by a shift to warmer droplet freezing temperatures by ~2-3°C. The changes in the aerosol's chemical composition during aging were observed using a laser ablation single-particle mass spectrometer and a soot-particle aerosol mass spectrometer. We will report our observations of the effects of other types of simulated aging (including photochemistry under high and low NOx conditions, dark ozonolysis, and nitric acid exposure) on Sawgrass and BBA from other grass and palm fuels.

  1. Hygroscopic, Morphological, and Chemical Properties of Agricultural Aerosols

    NASA Astrophysics Data System (ADS)

    Hiranuma, N.; Brooks, S. D.; Cheek, L.; Thornton, D. C.; Auvermann, B. W.; Littleton, R.

    2007-12-01

    Agricultural fugitive dust is a significant source of localized air pollution in the semi-arid southern Great Plains. In the Texas Panhandle, daily episodes of ground-level fugitive dust emissions from the cattle feedlots are routinely observed in conjunction with increased cattle activity in the late afternoons and early evenings. We conducted a field study to characterize size-selected agricultural aerosols with respect to hygroscopic, morphological, and chemical properties and to attempt to identify any correlations between these properties. To explore the hygroscopic nature of agricultural particles, we have collected size-resolved aerosol samples using a cascade impactor system at a cattle feedlot in the Texas Panhandle and have used the Environmental Scanning Electron Microscope (ESEM) to determine the water uptake by individual particles in those samples as a function of relative humidity. To characterize the size distribution of agricultural aerosols as a function of time, A GRIMM aerosol spectrometer and Sequential Mobility Particle Sizer and Counter (SMPS) measurements were simultaneously performed in an overall size range of 11 nm to 20 µm diameters at a cattle feedlot. Complementary determination of the elemental composition of individual particles was performed using Energy Dispersive X-ray Spectroscopy (EDS). In addition to the EDS analysis, an ammonia scrubber was used to collect ammonia and ammonium in the gas and particulate phases, respectively. The concentration of these species was quantified offline via UV spectrophotometry at 640 nanometers. The results of this study will provide important particulate emission data from a feedyard, needed to improve our understanding of the role of agricultural particulates in local and regional air quality.

  2. Infrared properties of atmospheric aerosol constituents. Polyaromatic hydrocarbons and terpenes

    SciTech Connect

    Sutherland, R.A. ); Khanna, R.K.; Ospina, M.J. )

    1994-01-01

    The infrared spectra (2-20 [mu]m) of six terpene samples and six polyaromatic hydrocarbon (PAH) samples are presented and compared with similar spectra obtained from standard grade petroleum (fog oil) samples. The selected samples are representative of the various different molecular structures that may be present in atmospheric aerosol sources, particularly fire smokes. Results are presented in terms of the wavelength-dependent complex refractive indices as obtained from bulk phase (thin layer) transmittance measurements and the Kramers-Kronig relationships. All samples exhibit a characteristic complex absorption spectra with numerous line absorption features in the 8-14-[mu]m atmospheric window regions with peak imaginary indices nominally around 0.10-0.12 for the terpene samples and on the order of 1.0-1.2 for the PAH samples, although there are far fewer lines in the PAH samples than in the terpene samples. The terpene also exhibit absorption features in the 3-5 [mu]m window which are much like those found in the standard samples but are not observed in the PAH samples. 24 refs., 4 figs., 1 tab.

  3. High sensitivity of Indian summer monsoon to Middle East dust absorptive properties

    NASA Astrophysics Data System (ADS)

    Jin, Qinjian; Yang, Zong-Liang; Wei, Jiangfeng

    2016-07-01

    The absorptive properties of dust aerosols largely determine the magnitude of their radiative impacts on the climate system. Currently, climate models use globally constant values of dust imaginary refractive index (IRI), a parameter describing the dust absorption efficiency of solar radiation, although it is highly variable. Here we show with model experiments that the dust-induced Indian summer monsoon (ISM) rainfall differences (with dust minus without dust) change from ‑9% to 23% of long-term climatology as the dust IRI is changed from zero to the highest values used in the current literature. A comparison of the model results with surface observations, satellite retrievals, and reanalysis data sets indicates that the dust IRI values used in most current climate models are too low, tending to significantly underestimate dust radiative impacts on the ISM system. This study highlights the necessity for developing a parameterization of dust IRI for climate studies.

  4. High sensitivity of Indian summer monsoon to Middle East dust absorptive properties

    PubMed Central

    Jin, Qinjian; Yang, Zong-Liang; Wei, Jiangfeng

    2016-01-01

    The absorptive properties of dust aerosols largely determine the magnitude of their radiative impacts on the climate system. Currently, climate models use globally constant values of dust imaginary refractive index (IRI), a parameter describing the dust absorption efficiency of solar radiation, although it is highly variable. Here we show with model experiments that the dust-induced Indian summer monsoon (ISM) rainfall differences (with dust minus without dust) change from −9% to 23% of long-term climatology as the dust IRI is changed from zero to the highest values used in the current literature. A comparison of the model results with surface observations, satellite retrievals, and reanalysis data sets indicates that the dust IRI values used in most current climate models are too low, tending to significantly underestimate dust radiative impacts on the ISM system. This study highlights the necessity for developing a parameterization of dust IRI for climate studies. PMID:27465689

  5. High sensitivity of Indian summer monsoon to Middle East dust absorptive properties.

    PubMed

    Jin, Qinjian; Yang, Zong-Liang; Wei, Jiangfeng

    2016-01-01

    The absorptive properties of dust aerosols largely determine the magnitude of their radiative impacts on the climate system. Currently, climate models use globally constant values of dust imaginary refractive index (IRI), a parameter describing the dust absorption efficiency of solar radiation, although it is highly variable. Here we show with model experiments that the dust-induced Indian summer monsoon (ISM) rainfall differences (with dust minus without dust) change from -9% to 23% of long-term climatology as the dust IRI is changed from zero to the highest values used in the current literature. A comparison of the model results with surface observations, satellite retrievals, and reanalysis data sets indicates that the dust IRI values used in most current climate models are too low, tending to significantly underestimate dust radiative impacts on the ISM system. This study highlights the necessity for developing a parameterization of dust IRI for climate studies. PMID:27465689

  6. Physical and Chemical Properties of Anthropogenic Aerosols: An Overview

    EPA Science Inventory

    Aerosol chemical composition is complex. Combustion aerosols can comprise tens of thousands of organic compounds, refractory brown and black carbon, heavy metals, cations, anions, salts, and other inorganic phases. Aerosol organic matter normally contains semivolatile material th...

  7. Long term measurements of atmospheric aerosol optical properties in the Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Kalivitis, N.; Bougiatioti, A.; Kouvarakis, G.; Mihalopoulos, N.

    2011-11-01

    Optical properties of atmospheric aerosol particles have been recorded at a remote location of the Eastern Mediterranean on a continuous basis since 2000. Measurements of aerosol scattering coefficient (bsp) and absorption coefficient (bap) have been conducted, providing the longest data series of such ground based measurements in the Eastern Mediterranean basin. bsp shows an annual cycle with maximum values observed during summer and minimum during winter. In addition, in periods when mineral dust is transported into the area, high values are observed. It has been shown that both the level and the annual variation of bsp can be well represented if ammonium sulfate (AS) and particulate organic matter (POM) are assumed as the only scattering species in the aerosol phase. bap was measured at three wavelengths using two different instruments and a single wavelength data series was extracted. Maximum values of bap were observed during summer and during periods with extended dust transport to the area. If mineral dust particles are present in the atmosphere they can contribute up to 80% of bap levels at the visible wavelengths.

  8. 2014 iAREA campaign on aerosol in Spitsbergen - Part 1: Study of physical and chemical properties

    NASA Astrophysics Data System (ADS)

    Lisok, J.; Markowicz, K. M.; Ritter, C.; Makuch, P.; Petelski, T.; Chilinski, M.; Kaminski, J. W.; Becagli, S.; Traversi, R.; Udisti, R.; Rozwadowska, A.; Jefimow, M.; Markuszewski, P.; Neuber, R.; Pakszys, P.; Stachlewska, I. S.; Struzewska, J.; Zielinski, T.

    2016-09-01

    This paper presents the results of measurements of aerosol physical and chemical properties during iAREA2014 campaign that took place on Svalbard between 15th of Mar and 4th of May 2014. With respect to field area, the experiment consisted of two sites: Ny-Ålesund (78°55‧N, 11°56‧E) and Longyearbyen (78°13‧N, 15°33‧E) with further integration of Aerosol Robotic Network (AERONET) station in Hornsund (77°00‧N, 15°33‧E). The subject of this study is to investigate the in-situ, passive and active remote sensing observations as well as numerical simulations to describe the temporal variability of aerosol single-scattering properties during spring season on Spitsbergen. The retrieval of the data indicates several event days with enhanced single-scattering properties due to the existence of sulphate and additional sea-salt load in the atmosphere which is possibly caused by relatively high wind speed. Optical results were confirmed by numerical simulations made by the GEM-AQ model and by chemical observations that indicated up to 45% contribution of the sea-salt to a PM10 total aerosol mass concentration. An agreement between the in-situ optical and microphysical properties was found, namely: the positive correlation between aerosol scattering coefficient measured by the nephelometer and effective radius obtained from laser aerosol spectrometer as well as negative correlation between aerosol scattering coefficient and the Ångstrom exponent indicated that slightly larger particles dominated during special events. The in-situ surface observations do not show any significant enhancement of the absorption coefficient as well as the black carbon concentration which might occur during spring. All of extensive single-scattering properties indicate a diurnal cycle in Longyearbyen, where 21:00-5:00 data stays at the background level, however increasing during the day by the factor of 3-4. It is considered to be highly connected with local emissions originating

  9. Diurnal Evolution of Aerosol Optical Properties and Morphology at Pico Tres Padres: A Phenomenological Analysis

    NASA Astrophysics Data System (ADS)

    Mazzoleni, C.; Chakrabarty, R.; Dubey, M. K.; Moosmuller, H.; Chylek, P.; Onasch, T. B.; Herndon, S.; Zavala, M.; Kolb, C.

    2007-05-01

    Aerosol optical properties affect planetary radiative balance and therefore climate. The optical properties are related to chemical composition, size distribution, and morphology, which also have implications for human health and environmental degradation. During the MILAGRO field campaign, we measured ensemble aerosol absorption and angle-integrated scattering in Mexico City. These measurements were performed using the Los Alamos aerosol photoacoustic instrument with an integrated nephelometer (LAPA) operating at 781 nm. The LAPA was mounted on-board the Aerodyne Inc. mobile laboratory, which hosted a wide variety of gaseous and aerosol instruments. During the campaign, the Aerodyne mobile laboratory was moved to different sites, capturing the influence of spatial and temporal parameters including location, aging, elevation, and sources on ambient air pollution. The LAPA operated almost continuously between the 3rd and the 28th of March 2006. During the same period we collected ambient aerosols on more than 100 Nuclepore filters for scanning electron microscopy (SEM) analysis. Filter samples were collected during specific pollution events and different times of the day. Subsequently, SEM images of selected filters were taken to study particle morphology. The elemental composition of a few individual particles was also qualitatively assessed by energy dispersive X-ray spectroscopy. Between March 7th and 19th the laboratory was sampling air close to the top of the Pico Tres Padres, a ~3000 m high mountain on the north side of the Mexico City. Daily changes of aerosol loading and pollutant concentrations followed the expected diurnal variations of the boundary layer height. Here we report a preliminary analysis of aerosol absorption, scattering, and morphology at Pico Tres Padres for three specific days (9th, 11th and 12th of March 2006). The single scattering albedo (ratio of scattering to total extinction) during these three days showed a characteristic drop in the

  10. Remote Sensing of Aerosol and Cloud Properties from Ground Based and Satellite Remote Sensors to Explore Aerosol-Cloud Interaction

    NASA Astrophysics Data System (ADS)

    He, Yuzhe

    The measurements of both aerosol and cloud properties are critical for climate studies since these mechanisms have the largest uncertainty in energy balance calculations. In addition, aerosols and clouds do not act independently but can significantly couple to each other. It is clear that being able to quantify these interactions is crucial to climate models. While there are many possible aerosol-cloud interactions, we limit our investigation to the Twomey indirect effect which relates how aerosols can modify the physical properties of clouds thereby changing the radiative properties. Verifying and quantifying such mechanisms on a global scale requires accurate measurements of both aerosols and clouds from satellites. Unfortunately, assessing this mechanism has been very difficult from satellites since both aerosols and cloud properties would have to be simultaneously measured. Therefore, only statistical approaches have been tried but it is easy to see that such approaches will tend to obscure the interpretation of local interaction mechanisms. In this thesis, we investigate the potential of both satellites and ground based approaches to measure Aerosol Cloud Interaction parameters. After assessing the limitations of satellite based approaches, we focus on the use of ground based remote sensing using a combination of Lidar, Microwave radiometry, Doppler Lidar and sky radiometry. This instrumentation suite offers a more direct approach that can probe the properties of both aerosols and clouds simultaneously allowing us to investigate real time aerosol-cloud processes which occur on time scale < 1 minute. To this end, we first provide a thorough description of the multi-sensor approach and how it can be implemented including a sensitivity analysis taking into account both atmospheric and surface variability as well as uncertainty in both the Liquid Water Path (LWP) and diffuse transmittance measurements. In addition, we use the Southern Great Plain (SGP) data to

  11. Aerosols optical properties in Titan's Detached Haze Layer

    NASA Astrophysics Data System (ADS)

    Seignovert, Benoit; Rannou, Pascal; Lavvas, Panayotis; West, Robert

    2016-10-01

    Titan's Detached Haze Layer (DHL) was first observed in 1983 by Rages and Pollack during the Voyager 2 is a consistent spherical haze feature surrounding Titan's upper atmosphere and detached from the main haze. Since 2005, the Imaging Science Subsystem (ISS) instrument on board the Cassini mission performs a continuous survey of the Titan's atmosphere and confirmed its persistence at 500 km up to the equinox (2009) before its drop and disappearance in 2012 (West et al. 2011). Previous analyses showed, that this layer corresponds to the transition area between small spherical aerosols and large fractal aggregates and play a key role in the aerosols formation in Titan's atmosphere (Rannou et al. 2000, Lavvas et al. 2009, Cours et al. 2011).In this talk we will present the UV photometric analyses based on radiative transfer inversion to retrieve aerosols particles properties in the DHL (bulk and monomer radius and local density) performed on ISS observations taken from 2005 to 2007.References:- Rages and Pollach, Icarus 55 (1983)- West, et al., Icarus 38 (2011)- Rannou, et al., Icarus 147 (2000)- Lavvas, et al., Icarus 201 (2009)- Cours, et al., ApJ Lett. 741 (2015)

  12. Chemical and physicochemial properties of submicron aerosol agglomerates

    SciTech Connect

    Scripsick, R.C.; Ehrman, S.; Friedlander, S.K.

    1998-12-31

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory. The formation of nanometer-sized aerosol particles in a premixed methane flame from both solid-phase aerosol precursors and gas-phase precursors was investigated. Techniques were developed to determine the distribution of the individual chemical species as a function of agglomerate size by using inductively coupled plasma atomic emission spectroscopy (ICP-AES). To determine the distribution of chemical species both from particle to particle and within the particl